RESUMEN
In addition to their well-known classical effects, cannabinoid CB1 and CB2 receptors have also been involvement in both deleterious and protective actions on the heart under various pathological conditions. While the potential therapeutic applications of the endocannabinoid system in the context of cardiovascular function are indeed a viable prospect, significant debate exists within the literature regarding whether CB1, CB2, or a combination of both receptors exert a favorable influence on cardiac function. Hence, the aim of this study was to investigate the effects of CB1 + CB2 or CB2 agonists on cardiac excitation-contraction (E-C) coupling, utilizing fish (Brycon amazonicus) as an experimental model. The CB2 agonist elicited marked positive inotropic and lusitropic responses in isolated ventricular myocardium, induced cyclic adenosine 3',5'-monophosphate (cAMP) production, and upregulated critical Ca2+ handling proteins, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and Na+/Ca2+ exchanger (NCX). Our current study demonstrated, for the first time, that CB2 receptor activation-induced effects improved the efficiency of Ca2+ cycling, excitation-contraction coupling (E-C coupling), and cardiac performance in under physiological conditions. Hence, CB2 receptors could be considered a potential therapeutic target for modulating cardiac contractile dysfunctions.
Asunto(s)
Cannabinoides , Characiformes , Animales , Receptores de Cannabinoides/metabolismo , Miocardio/metabolismo , Corazón , Acoplamiento Excitación-Contracción , Agonistas de Receptores de Cannabinoides/metabolismo , Agonistas de Receptores de Cannabinoides/farmacología , Receptor Cannabinoide CB2/metabolismo , Receptor Cannabinoide CB1/metabolismoRESUMEN
Fipronil is widely used as a broad-spectrum insecticide in agriculture, urban environments, and veterinary medicine. Fipronil can enter aquatic ecosystems and spread to sediment and organic matter, representing a risk to non-target species. This study aimed to evaluate the effects of short-term (96 h) exposure to a low and realistic concentration of sediment-associated fipronil (4.2 µg.kg-1 of Regent® 800 WG) on myocardial contractility of armored catfish Hypostomus regain, a benthic fish species. Fipronil exposure induced increased inotropism and acceleration of contractile kinetics, although no alterations in the relative ventricular mass were observed. This better cardiac function was associated with an elevated expression and/or function of the Na+/Ca2+ exchanger and its marked contribution to contraction and relaxation, probably due to a stress-induced adrenergic stimulation. Ventricle strips of exposed fish also exhibited a faster relaxation and a higher cardiac pumping capacity, indicating that armored catfish were able to perform cardiac adjustments to face the exposure. However, a high energetic cost to maintain an increased cardiac performance can make fish more susceptible to other stressors, impairing developmental processes and/or survival. These findings highlight the need for regulations of emerging contaminants, such as fipronil, to ensure adequate protection of the aquatic system.
Asunto(s)
Bagres , Animales , Ecosistema , Corazón , Pirazoles/toxicidadRESUMEN
This study investigated the dependence of contraction from extracellular Ca2+, the presence of a functional sarcoplasmic reticulum (SR), and the effects of ß-adrenergic stimulation using isometric cardiac muscle preparations. Moreover, the expression of Ca2+-handling proteins such as SR-Ca2+-ATPase (SERCA), phospholamban (PLN), and Na+/Ca2+ exchanger (NCX) were also evaluated in the ventricular tissue of adult African sharptooth catfish, Clarias gariepinus, a facultative air-breathing fish. In summary, we observed that (1) contractility was strongly regulated by extracellular Ca2+; (2) inhibition of SR Ca2+-release by application of ryanodine reduced steady-state force production; (3) ventricular myocardium exhibited clear post-rest decay, even in the presence of ryanodine, indicating a decrease in SR Ca2+ content and NCX as the main pathway for Ca2+ extrusion; (4) a positive force-frequency relationship was observed above 60 bpm (1.0 Hz); (5) ventricular tissue was responsive to ß-adrenergic stimulation, which caused significant increases in twitch force, kept a linear force-frequency relationship from 12 to 96 bpm (0.2 to Hz), and improved the cardiac pumping capacity (CPC); and (6) African catfish myocardium exhibited similar expression patterns of NCX, SERCA, and PLN, corroborating our findings that both mechanisms for Ca2+ transport across the SR and sarcolemma contribute to Ca2+ activator. In conclusion, this fish species displays great physiological plasticity of E-C coupling, able to improve the ability to maintain cardiac performance under physiological conditions to ecological and/or adverse environmental conditions, such as hypoxic air-breathing activity.
Asunto(s)
Adrenérgicos/farmacología , Calcio , Bagres , Contracción Miocárdica , Retículo Sarcoplasmático , Animales , Calcio/metabolismo , Bagres/metabolismo , Rianodina , Retículo Sarcoplasmático/metabolismo , ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico/metabolismo , Intercambiador de Sodio-CalcioRESUMEN
Pythons are important models of studies on postprandial metabolism because their physiological responses are exacerbated when digesting large prey. Prior studies of these animals have shown hypertrophy of the cardiac tissue 2 to 3â¯days after feeding, coinciding with the peak of the specific dynamic action (SDA), but the consequences of this remodeling in myocardial contractility have not been studied, which is the purpose of this work. Specimens of Python molurus were divided into two groups: a Digesting group (2â¯days after feeding, at the peak of SDA), and a Fasting group (28â¯days after feeding). When compared to the Fasting group, the Digesting group showed higher relative ventricular mass and calcium-handling protein expression such as sarcoplasmic reticulum Ca2+-ATPase (SERCA), phospholamban (PLB), and the Na+/Ca2+ exchanger (NCX). Digesting pythons also exhibited significant increases in the cardiac contraction force (Fc), rates of force development and relaxation, and cardiac pumping capacity. Therefore, the higher SERCA, PLB and NCX expression levels increased cytosolic Ca2+ transient amplitude, improving myofilament force. These changes are crucial to maintain cardiac output and a relatively high and continuous blood flow required by metabolic expenditure that occurs in postprandial animals.
Asunto(s)
Boidae/fisiología , Proteínas de Unión al Calcio/biosíntesis , Conducta Alimentaria/fisiología , Contracción Miocárdica/fisiología , Miocardio/metabolismo , Proteínas de Reptiles/biosíntesis , Animales , MianmarRESUMEN
Microcystin's (MCs) are toxins produced by several groups of cyanobacteria, in water bodies throughout the world, in a process which is being intensified by human action. Among the variants of MCs, MC-LR stands out for its distribution and toxicity. MCs are potent inhibitors of protein phosphatases 1 and 2 A, which causes disruption of the cytoskeleton and consequent cell death. They can also alter the antioxidant system and induce oxidative stress in various organs of many species. There is, however, a lack of information about the effects of MCs on the antioxidant system and oxidative damage in Brazilian fishes. This study evaluated the effect of microcystin-LR on the antioxidant system in liver and gills of the Brazilian fish Brycon amazonicus, after 48 h of i.p injection of 100 µg MC-LR.kg-1 body mass. The liver exhibited increases in the activity of GST (74%) and GPx (217%), and a 47% decrease in SOD activity, with no changes in CAT values. In the gills of fish exposed to MC-LR, CAT and GPx activities did not show significant changes, while SOD and GST activity decreased by 66% and 37%, respectively. The GSH content did not change significantly in the liver, however, a decrease of 43% was observed in the gills. Oxidative damage measured by protein oxidation (PC) and lipoperoxidation (LPO) showed significant effects in both tissues. In hepatic tissue, there was no change in PC levels but LPO increased by 116%. Conversely, in the gills LPO levels did not change but PC increased by 317%. In conclusion, these data show that MC-LR induces oxidative damage in both tissues but in different ways, with being liver most sensitive to LPO and gills to PC. This also suggests that the gills are most sensitive to oxidative stress than liver, due to the inhibition of its antioxidant responses following MC-LR exposure.
Asunto(s)
Characiformes , Branquias/efectos de los fármacos , Hígado/efectos de los fármacos , Microcistinas/toxicidad , Animales , Antioxidantes/metabolismo , Brasil , Branquias/enzimología , Inyecciones Intraperitoneales , Peroxidación de Lípido/efectos de los fármacos , Hígado/enzimología , Toxinas Marinas , Estrés OxidativoRESUMEN
Matrinxã (Brycon amazonicus) is a great swimming performance teleost fish from the Amazon basin. However, the possible cardiac adaptations of this ability are still unknown. Therefore, the aim of the present work was to investigate the effects of prolonged exercise (EX group - 60days under 0.4BL·s-1) on ventricular contractility by (i) in-vitro analysis of contractility comparing the relative roles of sodium/calcium exchanger (NCX) and sarcoplasmic reticulum (SR) in the excitation-contraction (E-C) coupling and (ii) molecular analysis of NCX, sarcoplasmic reticulum Ca2+ ATPase (SERCA2) and phospholamban (PLB) expression and quantification. The exercise training significantly improved twitch tension, cardiac pumping capacity and the contraction rate when compared to controls (CT). Inhibition of the NCX function, replacing Na+ by Li+ in the physiological solutions, diminished cardiac contractility in the EX group, reduced all analyzed parameters under both high and low stimulation frequencies. The SR blockage, using 10µM ryanodine, caused ~50% tension reduction in CT at most analyzed frequencies while in EX, reductions (34-54%) were only found at higher frequencies. SR inhibition also decreased contraction and relaxation rates in both groups. Additionally, higher post-rest contraction values were recorded for EX, indicating an increase in SR Ca2+ loading. Higher NCX and PLB expression rates and lower SERCA2 rates were found in EX. Our data indicate that matrinxã presents a modulation in E-C coupling after exercise-training, enhancing the SR function under higher frequencies. This was the first study to functionally analyze the effects of swimming-induced exercise on fish cardiac E-C coupling.
Asunto(s)
Señalización del Calcio , Characiformes/fisiología , Acoplamiento Excitación-Contracción , Regulación del Desarrollo de la Expresión Génica , Corazón/fisiología , Miocardio/metabolismo , Condicionamiento Físico Animal , Animales , Acuicultura , Brasil , Bloqueadores de los Canales de Calcio/farmacología , Señalización del Calcio/efectos de los fármacos , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Characiformes/crecimiento & desarrollo , Acoplamiento Excitación-Contracción/efectos de los fármacos , Tolerancia al Ejercicio , Proteínas de Peces/antagonistas & inhibidores , Proteínas de Peces/genética , Proteínas de Peces/metabolismo , Corazón/efectos de los fármacos , Corazón/crecimiento & desarrollo , Miocardio/enzimología , Tamaño de los Órganos , Distribución Aleatoria , Retículo Sarcoplasmático/efectos de los fármacos , Retículo Sarcoplasmático/enzimología , Retículo Sarcoplasmático/metabolismo , ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico/genética , ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico/metabolismo , Intercambiador de Sodio-Calcio/antagonistas & inhibidores , Intercambiador de Sodio-Calcio/genética , Intercambiador de Sodio-Calcio/metabolismo , Natación , Movimientos del AguaRESUMEN
Alternagin-C (ALT-C) is a disintegrin-like protein isolated from Rhinocerophis alternatus snake venom, which induces endothelial cell proliferation and angiogenesis. The aim of this study was to evaluate the systemic effects of a single dose of alternagin-C (0.5 mg·kg-1, via intra-arterial) on oxidative stress biomarkers, histological alterations, vascular endothelial growth factor (VEGF) production, and the degree of vascularization in the liver of the freshwater fish traíra, Hoplias malabaricus, seven days after the initiation of therapy. ALT-C treatment increased VEGF levels and hepatic angiogenesis. ALT-C also enhanced hepatic antioxidant enzymes activities such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, decreasing the basal oxidative damage to lipids and proteins in the fish liver. These results indicate that ALT-C improved hepatic tissue and may play a crucial role in tissue regeneration mechanisms.
Asunto(s)
Characiformes/metabolismo , Desintegrinas/farmacología , Hígado/efectos de los fármacos , Neovascularización Fisiológica/efectos de los fármacos , Animales , Vasos Sanguíneos/efectos de los fármacos , Bothrops , Catalasa/metabolismo , Characiformes/fisiología , Venenos de Crotálidos , Glutatión/metabolismo , Glutatión Peroxidasa/metabolismo , Glutatión Reductasa/metabolismo , Glutatión Transferasa/metabolismo , Hígado/irrigación sanguínea , Hígado/metabolismo , Estrés Oxidativo/efectos de los fármacos , Superóxido Dismutasa/metabolismo , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
Glyphosate-based herbicides are widely used in agriculture and are commonly found in water bodies. Roundup Original(®) (RO) contains an isopropylamine glyphosate (GLY) salt containing the surfactant POEA, while Roundup Transorb R(®) (RTR) contains a potassium salt of GLY with unknown surfactants. Both contain different compositions of so-called "inert" ingredients, more toxic than glyphosate. Amphibian tadpoles often experience variations in O2 availability in their aquatic habitats; an ability to tolerate hypoxia can condition their survival and fitness. We evaluated the impacts of sublethal concentrations of GLY (1 mg L(-1)), RO (1 mg L(-1) GLY a.e) and RTR (1 mg L(-1) GLY a.e) on metabolic rate (V·O2 - mLO2 Kg1 h(-1)) of bullfrog tadpoles during normoxia and graded hypoxia, and related this to morphology of their skin, their major site of gas exchange. In control (CT) V·O2 remained unaltered from normoxia until 40 mmHg, indicating a critical O2 tension between 40 and 20 mmHg. GLY significantly reduced V·O2, possibly due to epidermal hypertrophy, which increased O2 diffusion distance to O2 uptake. In contrast, RTR increased V·O2 during hypoxia, indicating an influence of "inert" compounds and surfactants. V·O2 of RO did not differ from CT, suggesting that any increase in V·O2 caused by exposure was antagonized by epidermal hypertrophy. Indeed, all herbicides caused marked alterations in skin morphology, with cell and epithelium wall presenting hyperplasia or hypertrophy and chromatid rupture. In summary, GLY, RO and RTR exert different effects in bullfrog tadpoles, in particular the surfactants and inert compounds appear to influence oxygen uptake.
Asunto(s)
Glicina/análogos & derivados , Herbicidas/toxicidad , Larva/efectos de los fármacos , Rana catesbeiana , Tensoactivos/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Glicina/toxicidad , Larva/anatomía & histología , Larva/metabolismo , Oxígeno/metabolismo , Rana catesbeiana/anatomía & histología , Rana catesbeiana/metabolismo , Piel/efectos de los fármacos , Piel/patología , GlifosatoRESUMEN
The baroreflex is one of the most important regulators of cardiovascular homeostasis in vertebrates. It begins with the monitoring of arterial pressure by baroreceptors, which constantly provide the central nervous system with afferent information about the status of this variable. Any change in arterial pressure relative to its normal state triggers autonomic responses, which are characterized by an inversely proportional change in heart rate and systemic vascular resistance and which tend to restore pressure normality. Although the baroreceptors have been located in mammals and other terrestrial vertebrates, their location in fish is still not completely clear and remains quite controversial. Thus, the objective of this study was to locate the baroreceptors in a teleost, the Colossoma macropomum. To do so, the occurrence and efficiency of the baroreflex were both analyzed when this mechanism was induced by pressure imbalancements in intact fish (IN), first-gill-denervated fish (G1), and total-gill-denervated fish (G4). The pressure imbalances were initiated through the administration of the α1-adrenergic agonist phenylephrine (100 µg kg(-1)) and the α1-adrenergic antagonist prazosin (1 mg kg(-1)). The baroreflex responses were then analyzed using an electrocardiogram that allowed for the measurement of the heart rate, the relationship between pre- and post-pharmacological manipulation heart rates, the time required for maximum chronotropic baroreflex response, and total heart rate variability. The results revealed that the barostatic reflex was attenuated in the G1 group and nonexistent in G4 group, findings which indicate that baroreceptors are exclusively located in the gill arches of C. macropomum.
Asunto(s)
Barorreflejo , Peces/fisiología , Branquias/inervación , Branquias/fisiología , Agonistas de Receptores Adrenérgicos alfa 1/farmacología , Antagonistas de Receptores Adrenérgicos alfa 1/farmacología , Animales , Presión Arterial , Desnervación , Electrocardiografía , Femenino , Frecuencia Cardíaca , Masculino , Fenilefrina/farmacología , Prazosina/farmacología , ReflejoRESUMEN
The growing Hg input in aquatic environments results in high accumulation of mercury in fish tissue and their consumers, which poses a serious risk to humans and ecosystems. The aim of this study was to evaluate the effects of the inorganic mercury exposure on cardiorespiratory responses in two species of neotropical fish ecologically distinct, matrinxã (Brycon amazonicus) and traíra (Hoplias malabaricus). Matrinxãs were exposed to a nominal and sublethal concentration of 0.15 mgL(-1) of HgCl2 for 96 h. Traíras were exposed to trophic doses (each 4 days, during 30 days) of inorganic Hg (0.45 mg as total Hg) using juvenile B. amazonicus as prey vehicle. The metabolic rate (VO2), critical oxygen tensions (PcO2), gill ventilation (VG), tidal volume (VT), respiratory frequency (fR), O2 extraction from the ventilatory current (EO2), and heart rate (fH) were measured under normoxia (140 mm Hg) and graded hypoxia (120, 100, 80, 60, 40, 20, and 10 mm Hg). Regarding matrinxã specifically, the critical point highlighted was tachypnea. In traíras, bradypnea, decreased metabolic rate and O2 extraction, severe bradycardia, and elevated tidal volume were observed in normoxia. Both acute and sub-chronic exposures increased the critical tension of O2 values in more than 100%. In addition, Hg exposures modulated hypoxia-induced responses resulting in impairment of cardio-respiratory system of both species. Thus, mercury, via food or water, decreases the plasticity of the cardiorespiratory responses reducing the survival chances of B. amazonicus and H. malabaricus under hypoxic conditions frequently observed in theirs wild habitats.
Asunto(s)
Characidae/fisiología , Corazón/efectos de los fármacos , Mercurio/toxicidad , Sistema Respiratorio/efectos de los fármacos , Animales , Metabolismo Basal/efectos de los fármacos , Branquias/efectos de los fármacos , Frecuencia Cardíaca/efectos de los fármacos , Hipoxia/fisiopatología , Consumo de Oxígeno/efectos de los fármacos , Frecuencia Respiratoria/efectos de los fármacosRESUMEN
This study evaluated the effects of trophic and subchronic exposure to inorganic mercury (Hg) on the oxidative stress biomarkers and its bioaccumulation potential in the liver, gills, white muscle and heart of the freshwater top predator fish, Hoplias malabaricus, fed with contaminated live juveniles of matrinxã, Brycon amazonicus, as prey vehicle. Inorganic mercury increased superoxide dismutase, catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase, and glutathione reductase (GR) activities in the liver, white muscle and heart. Gills CAT activity remained unchanged while GPx and GR values showed a significant decrease. In the liver and gills, Hg induced significant increase in the reduced (GSH) and oxidized (GSSG) glutathione content, concomitantly with a significant decrease in [GSH]/[GSSG] ratio. Differently, in cardiac tissue, the Hg caused an increase in GSH level and increase in [GSH]/[GSSG] ratio. Lipid and protein oxidation and metallothionein levels were significantly higher after Hg trophic exposure in the liver, gills and heart, but remained at control values in the white muscle. Tissue-specific responses against oxidative stress were observed, and the liver and gills were the most sensitive organs, showing signs of redox homeostasis failure. At the end of the experiment, dietary inorganic mercury accumulated through food chain levels. In order, Hg bioaccumulation was: gills > liver >> white muscle = heart. These results pointed out the potential of inorganic Hg to bioaccumulate in aquatic systems. Taken together, our findings suggest that Hg, even in the inorganic form and sublethal amounts, is a risk factor for aquatic biota.
Asunto(s)
Characiformes/metabolismo , Mercurio/metabolismo , Estrés Oxidativo , Contaminantes Químicos del Agua/metabolismo , Animales , Biomarcadores/metabolismo , Catalasa/metabolismo , Exposición a Riesgos Ambientales , Proteínas de Peces/metabolismo , Cadena Alimentaria , Branquias/metabolismo , Glutatión Peroxidasa/metabolismo , Glutatión Reductasa/metabolismo , Glutatión Transferasa/metabolismo , Hígado/metabolismo , Fibras Musculares de Contracción Rápida/metabolismo , Miocardio/metabolismo , Superóxido Dismutasa/metabolismoRESUMEN
This study investigated the potentially detrimental effects of copper and elevated aquatic CO(2) (hypercarbia), alone or in combination, on pacu, Piaractus mesopotamicus. Fish were exposed for 48 h to control (no copper addition in normocarbia), to 400 µg Cu(2+)L(-1), to hypercarbic (1% CO(2); PCO(2) = 6.9 mm Hg) water and to 400 µg Cu(2+)L(-1) + hypercarbia. In liver the single factors caused an increase in lipid hydroperoxide concentration that was not observed when the factors were combined. Copper exposure elicited increased hepatic superoxide dismutase activity, irrespective of aquatic CO(2) level. On the other hand, the effects of copper on hepatic glutathione peroxidase activity were dependent on water CO(2) levels. The two stressors combined did not affect hepatic catalase activity. Hypercarbic water caused a decline in plasma glucose concentration, but this was not observed when hypercarbia was combined with copper exposure. Copper caused a decrease in branchial Na(+)/K(+)-ATPase activity that was independent of water CO(2) level. Copper caused an increase in branchial metallothionein concentration that was independent of water CO(2) level. Thus, branchial metallothionein and Na(+)/K(+)-ATPase were effective biomarkers of copper exposure that were not affected by water CO(2) level.
Asunto(s)
Antioxidantes/metabolismo , Dióxido de Carbono/metabolismo , Characidae/metabolismo , Cobre/toxicidad , Exposición a Riesgos Ambientales/análisis , Animales , Análisis Químico de la Sangre/métodos , Catalasa/metabolismo , Branquias/efectos de los fármacos , Branquias/enzimología , Branquias/metabolismo , Hígado/efectos de los fármacos , Hígado/enzimología , Hígado/metabolismo , Metalotioneína/metabolismo , Oxidación-Reducción , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Superóxido Dismutasa/metabolismo , Pruebas de Toxicidad/métodos , Contaminantes del Agua/toxicidadRESUMEN
Copper sulfate (CuSO(4))is an inorganic chemical product worldwide used as an algaecide and a fungicide in aquaculture and agriculture and being discharged into freshwater environments where it can affect the freshwater fauna, especially fishes. The impact of copper on fish cardiac function was analyzed in two groups of Nile tilapias, Oreochromis niloticus (control group and group exposed to 1 mg l(-1) of CuSO(4) for 96 h). Structural and ultra-structural changes were studied and related to perturbations of the inotropic and chronotropic responses of ventricle strips. Fish of Cu exposed group did not show significant alterations in the medium diameter and in the percentage of collagen in the cardiac myocytes when evaluated through the light microscope. However, the ultrastructural analysis revealed cellular swelling followed by mitochondrial swelling. The myofibrils did not show significant variations among groups. Force contraction was significantly decreased, and rates of time to tension increase (contraction) and decrease (relaxation) were significantly augmented after copper exposure. The results suggest that the copper sulfate impairs the oxidative mitochondrial function and consequently alters the cardiac performance of this species.
Asunto(s)
Cíclidos/fisiología , Sulfato de Cobre/toxicidad , Miocitos Cardíacos/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Animales , Colágeno/metabolismo , Femenino , Ventrículos Cardíacos/efectos de los fármacos , Ventrículos Cardíacos/patología , Ventrículos Cardíacos/fisiopatología , Procesamiento de Imagen Asistido por Computador , Masculino , Microscopía Electrónica de Transmisión , Mitocondrias Cardíacas/efectos de los fármacos , Mitocondrias Cardíacas/ultraestructura , Contracción Miocárdica/efectos de los fármacos , Contracción Miocárdica/fisiología , Miocitos Cardíacos/fisiología , Miocitos Cardíacos/ultraestructura , Miofibrillas/efectos de los fármacos , Miofibrillas/ultraestructuraRESUMEN
The effects of microcystin on the cardio-respiratory function of Nile tilapia were analyzed 48 h after intraperitoneal injection of microcystin-LR (MC-LR - 100 µg kg(-1)body weight). Exposure to MC-LR induced significant reduction in metabolic rate (VO(2)) and increase in the critical O(2) tension (P(C)O(2)) in relation to the control group. Gill ventilation (V(G)) and ventilatory tidal volume (V(T)) were considerably lower in fish exposed to MC-LR, probably due to an alteration in the homeostatic mechanisms, impairing the regular respiratory response of this species to environmental hypoxia. The ability to maintain the O(2) extraction from the ventilatory current (EO(2)) during severe hypoxia was also significantly reduced in fish exposed to MC-LR exposure. Control fish displayed the characteristic reflex bradycardia in response to hypoxia. However, when compared to the control group, fish exposed to MC-LR presented significantly lower heart rate (f(H)) in normoxia and in all experimental hypoxic levels, probably due to a direct effect of this toxin on the cardiac tissue.
Asunto(s)
Sistema Cardiovascular/efectos de los fármacos , Cíclidos/fisiología , Microcistinas/toxicidad , Sistema Respiratorio/efectos de los fármacos , Animales , Sistema Cardiovascular/metabolismo , Eutrofización , Agua Dulce/química , Toxinas Marinas , Oxígeno/análisis , Consumo de Oxígeno/efectos de los fármacos , Sistema Respiratorio/metabolismoRESUMEN
The aim of the present study was to determine the roles that externally versus internally oriented CO(2)/H(+)-sensitive chemoreceptors might play in promoting cardiorespiratory responses to environmental hypercarbia in the air-breathing fish, Hoplerythrinus unitaeniatus (jeju). Fish were exposed to graded hypercarbia (1, 2.5, 5, 10 and 20% CO(2)) and also to graded levels of environmental acidosis (pH approximately 7.0, 6.0, 5.8, 5.6, 5.3 and 4.7) equal to the pH levels of the hypercarbic water to distinguish the relative roles of CO(2) versus H(+). We also injected boluses of CO(2)-equilibrated solutions (5, 10 and 20% CO(2)) and acid solutions equilibrated to the same pH as the CO(2) boluses into the caudal vein (internal) and buccal cavity (external) to distinguish between internal and external stimuli. The putative location of the chemoreceptors was determined by bilateral denervation of branches of cranial nerves IX (glossopharyngeal) and X (vagus) to the gills. The data indicate that the chemoreceptors eliciting bradycardia, hypertension and gill ventilatory responses (increased frequency and amplitude) to hypercarbia are exclusively branchial, externally oriented and respond specifically to changes in CO(2) and not H(+). Those involved in producing the cardiovascular responses appeared to be distributed across all gill arches while those involved in the gill ventilatory responses were located primarily on the first gill arch. Higher levels of aquatic CO(2) depressed gill ventilation and stimulated air breathing. The chemoreceptors involved in producing air breathing in response to hypercarbia also appeared to be branchial, distributed across all gill arches and responded specifically to changes in aquatic CO(2). This would suggest that chemoreceptor groups with different orientations (blood versus water) are involved in eliciting air-breathing responses to hypercarbia in jeju.
Asunto(s)
Aire , Dióxido de Carbono/metabolismo , Células Quimiorreceptoras/metabolismo , Peces/fisiología , Hipercapnia/metabolismo , Reflejo/fisiología , Respiración , Animales , Fenómenos Fisiológicos Cardiovasculares , Células Quimiorreceptoras/citología , Desnervación , Branquias/inervación , Branquias/fisiología , Concentración de Iones de HidrógenoRESUMEN
In one series of experiments, heart frequency (f (H)), blood pressure (P (a)), gill ventilation frequency (f ( R )), ventilation amplitude (V (AMP)) and total gill ventilation (V (TOT)) were measured in intact jeju (Hoplerythrinus unitaeniatus) and jeju with progressive denervation of the branchial branches of cranial nerves IX (glossopharyngeal) and X (vagus) without access to air. When these fish were submitted to graded hypoxia (water PO(2) approximately 140, normoxia to 17 mmHg, severe hypoxia), they increased f ( R ), V (AMP), V (TOT) and P (a) and decreased f (H). In a second series of experiments, air-breathing frequency (f (RA)), measured in fish with access to the surface, increased with graded hypoxia. In both series, bilateral denervation of all gill arches eliminated the responses to graded hypoxia. Based on the effects of internal (caudal vein, 150 microg NaCN in 0.2 mL saline) and external (buccal) injections of NaCN (500 microg NaCN in 1.0 mL water) on f (R), V (AMP), V (TOT), P (a) and f (H) we conclude that the O(2) receptors involved in eliciting changes in gill ventilation and associated cardiovascular responses are present on all gill arches and monitor the O(2) levels of both inspired water and blood perfusing the gills. We also conclude that air breathing arises solely from stimulation of branchial chemoreceptors and support the hypothesis that internal hypoxaemia is the primary drive to air breathing.
Asunto(s)
Células Quimiorreceptoras/fisiología , Peces/fisiología , Branquias/fisiología , Frecuencia Cardíaca/fisiología , Hipoxia/fisiopatología , Consumo de Oxígeno/fisiología , Mecánica Respiratoria/fisiología , Animales , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Brasil , Nervios Craneales/cirugía , Desnervación , Branquias/citología , Frecuencia Cardíaca/efectos de los fármacos , Reflejo/fisiología , Mecánica Respiratoria/efectos de los fármacos , Cianuro de Sodio/farmacología , Taquicardia/fisiopatología , Factores de TiempoRESUMEN
Copper sulfate is widely used in aquaculture. Exposure to this compound can be harmful to fish, resulting in oxidative metabolism alterations and gill tissue damage. Pacu, Piaractus mesopotamicus, (wt = 43.4 +/- 3.35 g) were distributed in experimental tanks (n = 10; 180 l) and exposed for 48 h to control (without copper addition), 0.4Cu (0.4 mg l(-1)), 0CupH (without copper addition, pH = 5.0) and 0.4CupH (0.4 mg l(-1), pH = 5.0). In liver and red muscle, the superoxide dismutase (SOD) was responsive to the increases in the aquatic copper. The plasmatic intermediary metabolites and hematological variables in the fish of group 0.4Cu were similar to those of the control group. Conversely, the exposure to 0.4CupH caused an increase in the plasmatic lactate, number of red blood cells (RBC) and hemoglobin (Hb). Plasmatic copper concentration [Cu(p)] increased in group 0.4Cu and 0.4CupH, which is higher in group 0.4CupH, suggests an effect of water pH on the absorbed copper. Exposure to 0.4Cu and 0.4CupH resulted in a reduction in the Na(+)/K(+)-ATPase activity and an increase in metallothionein (MT) in the gills. Exposure to 0CupH caused a decrease in glucose and pyruvate concentrations and an increase in RBC, Hb, and the branchial Na(+)/K(+)-ATPase activity. These responses suggest that the fish triggered mechanisms to revert the blood acidosis, save energy and increase the oxygen uptake. MT was an effective biomarker, responding to copper in different pHs and dissolved oxygen. Combined-factors caused more significant disturbance in the biomarkers than single-factors.
Asunto(s)
Antioxidantes/metabolismo , Sulfato de Cobre/toxicidad , Peces , Contaminantes Químicos del Agua/toxicidad , Animales , Glucemia/efectos de los fármacos , Branquias/efectos de los fármacos , Branquias/metabolismo , Concentración de Iones de Hidrógeno , Estrés Oxidativo/efectos de los fármacos , Oxígeno/metabolismo , Ácido Pirúvico/sangre , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Superóxido Dismutasa/metabolismoRESUMEN
Alterations in the antioxidant cellular system have often been proposed as biomarkers of pollutant-mediated toxicity. This study evaluated the effects of mercury on oxidative stress biomarkers and bioaccumulation in the liver, gills, white muscle and heart of the freshwater fish matrinxã, Brycon amazonicus, exposed to a nominal and sub-lethal concentration (~20% of 96 h-LC(50)) of 0.15 mg L(-1) of mercury chloride (HgCl(2)) for 96 h in a static system. Increases in superoxide dismutase, catalase, glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were observed in all tissues after HgCl(2) exposure, except for white muscle GR activity and hepatic GPx. In the liver and gills, the exposure to HgCl(2) also induced significant increases in reduced glutathione (GSH). Conversely, exposure to HgCl(2) caused a significant decrease in the GSH levels and an increase in the oxidized glutathione (GSSG) content in the white muscle, while both GSH and GSSG levels increased significantly in the heart muscle. Metallothionein concentrations were significantly high after HgCl(2) exposure in the liver, gills and heart, but remained at control values in the white muscle. HgCl(2) exposure induced oxidative damage, increasing the lipid peroxidation and protein carbonyl content in all tissues. Mercury accumulated significantly in all the fish tissue. The pattern of accumulation follows the order gills > liver >> heart > white muscle. In conclusion, these data suggest that oxidative stress in response to inorganic mercury exposure could be the main pathway of toxicity induced by this metal in fish.
Asunto(s)
Peces/metabolismo , Cloruro de Mercurio/toxicidad , Estrés Oxidativo/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Animales , Brasil , Catalasa/metabolismo , Agua Dulce/química , Branquias/metabolismo , Glutatión Peroxidasa/metabolismo , Glutatión Reductasa/metabolismo , Glutatión Transferasa/metabolismo , Dosificación Letal Mediana , Peroxidación de Lípido/efectos de los fármacos , Hígado/metabolismo , Cloruro de Mercurio/farmacocinética , Músculos/metabolismo , Estadísticas no Paramétricas , Superóxido Dismutasa/metabolismo , Contaminantes Químicos del Agua/farmacocinéticaRESUMEN
This study analyzed the physiological role of the cardiac sarcoplasmic reticulum (SR) of two neotropical teleosts, the jeju, Hoplerythrinus unitaeniatus (Erythrinidae), and the acara, Geophagus brasiliensis (Cichlidae). While the in vivo heart frequency (fH - bpm) of acara (79.6 ± 6.6) was higher than that of the jeju (50.3 ± 2.7), the opposite was observed for the ventricular inotropism (Fc - mN/mm²) at 12 bpm (acara = 28.66 ± 1.86 vs. jeju = 36.09 ± 1.67). A 5 min diastolic pause resulted in a strong potentiation of Fc (≅ 90 percent) of strips from jeju, which was completely abolished by ryanodine. Ryanodine also resulted in a ≅ 20 percent decrease in the Fc developed by strips from jeju at both subphysiological (12 bpm) and physiological (in vivo) frequencies. However, this effect of ryanodine reducing the Fc from jeju was completely compensated by adrenaline increments (10-9 and 10-6 M). In contrast, strips from acara were irresponsive to ryanodine, irrespective of the stimulation frequency, and increases in adrenaline concentration (to 10-9 and 10-6 M) further increased Fc. These results reinforce the hypothesis of the functionality of the SR as a common trait in neotropical ostariophysian (as jeju), while in acanthopterygians (as acara) it seems to be functional mainly in 'athletic' species.(AU)
O presente estudo analisou o papel fisiológico desempenhado pelo retículo sarcoplasmático (RS) de duas espécies de teleósteos neotropicais, o jeju, Hoplerythrinus unitaeniatus (Erythrinidae), e o acará, Geophagus brasiliensis (Cichlidae). Enquanto a frequência cardíaca registrada in vivo (fH - bpm) para o acará (79.6 ± 6.6) foi superior àquela observada para o jeju (50.3 ± 2.7), resposta inversa foi verificada para o inotropismo ventricular (Fc - mN/mm²) na frequência de estimulação de 12 bpm (acará = 28.66 ± 1.86 vs. jeju = 36.09 ± 1.67). Uma pausa diastólica de 5 min resultou em uma expressiva potenciação da Fc (≅ 90 por cento) das tiras de jeju, a qual foi completamente abolida pela rianodina. A rianodina também resultou em um decréscimo de ≅ 20 por cento na Fc desenvolvida pelas tiras de jeju tanto a frequências sub-fisiológicas (12 bpm) quanto fisiológicas (in vivo). No entanto, o decréscimo da Fc promovido pela rianodina foi completamente compensado pela adição de adrenalina (10-9 e 10-6 M). Em contraste, as tiras de acará foram irresponsivas à rianodina, independentemente da frequência de estimulação utilizada, fazendo com que a adição de adrenalina (10-9 e 10-6 M) resultasse em incrementos ainda maiores da Fc. Esses resultados reforçam a hipótese de que a funcionalidade do RS seja uma característica comum aos ostariofíseos neotropicais (como o jeju), enquanto nos acantopterígios (como o acará) esta organela parece ser funcional principalmente em espécies ativas.(AU)
Asunto(s)
Animales , Acoplamiento Excitación-Contracción , Characiformes/anatomía & histología , Ventrículos Cardíacos/química , Contracción Miocárdica/fisiologíaRESUMEN
This study analyzed the physiological role of the cardiac sarcoplasmic reticulum (SR) of two neotropical teleosts, the jeju, Hoplerythrinus unitaeniatus (Erythrinidae), and the acara, Geophagus brasiliensis (Cichlidae). While the in vivo heart frequency (fH - bpm) of acara (79.6 ± 6.6) was higher than that of the jeju (50.3 ± 2.7), the opposite was observed for the ventricular inotropism (Fc - mN/mm²) at 12 bpm (acara = 28.66 ± 1.86 vs. jeju = 36.09 ± 1.67). A 5 min diastolic pause resulted in a strong potentiation of Fc (≅ 90 percent) of strips from jeju, which was completely abolished by ryanodine. Ryanodine also resulted in a ≅ 20 percent decrease in the Fc developed by strips from jeju at both subphysiological (12 bpm) and physiological (in vivo) frequencies. However, this effect of ryanodine reducing the Fc from jeju was completely compensated by adrenaline increments (10-9 and 10-6 M). In contrast, strips from acara were irresponsive to ryanodine, irrespective of the stimulation frequency, and increases in adrenaline concentration (to 10-9 and 10-6 M) further increased Fc. These results reinforce the hypothesis of the functionality of the SR as a common trait in neotropical ostariophysian (as jeju), while in acanthopterygians (as acara) it seems to be functional mainly in 'athletic' species.(AU)
O presente estudo analisou o papel fisiológico desempenhado pelo retículo sarcoplasmático (RS) de duas espécies de teleósteos neotropicais, o jeju, Hoplerythrinus unitaeniatus (Erythrinidae), e o acará, Geophagus brasiliensis (Cichlidae). Enquanto a frequência cardíaca registrada in vivo (fH - bpm) para o acará (79.6 ± 6.6) foi superior àquela observada para o jeju (50.3 ± 2.7), resposta inversa foi verificada para o inotropismo ventricular (Fc - mN/mm²) na frequência de estimulação de 12 bpm (acará = 28.66 ± 1.86 vs. jeju = 36.09 ± 1.67). Uma pausa diastólica de 5 min resultou em uma expressiva potenciação da Fc (≅ 90 por cento) das tiras de jeju, a qual foi completamente abolida pela rianodina. A rianodina também resultou em um decréscimo de ≅ 20 por cento na Fc desenvolvida pelas tiras de jeju tanto a frequências sub-fisiológicas (12 bpm) quanto fisiológicas (in vivo). No entanto, o decréscimo da Fc promovido pela rianodina foi completamente compensado pela adição de adrenalina (10-9 e 10-6 M). Em contraste, as tiras de acará foram irresponsivas à rianodina, independentemente da frequência de estimulação utilizada, fazendo com que a adição de adrenalina (10-9 e 10-6 M) resultasse em incrementos ainda maiores da Fc. Esses resultados reforçam a hipótese de que a funcionalidade do RS seja uma característica comum aos ostariofíseos neotropicais (como o jeju), enquanto nos acantopterígios (como o acará) esta organela parece ser funcional principalmente em espécies ativas.(AU)