RESUMEN
In animal models of acute ischemic stroke, intravenous dehydroascorbic acid (DHAA), unlike ascorbic acid (AA), readily enters brain and is converted in both normal and ischemic brain into protective ascorbic acid. When given parenterally DHAA minimizes infarct volume and facilitates functional recovery. I hypothesize the same effect will occur in humans with acute ischemic stroke. Efficacy in reducing infarct volume is demonstrable in mice and rats even when DHAA is infused three hours after the experimental infarct. Moreover, there is fivefold mechanistic rational for DHA beside excellent pharmacokinetics and rapid penetration of brain and conversion to protective AA: (1) in ischemic brain, there is a precipitous decline in AA which can be reversed by intravenous DHAA; (2) after reduction of DHAA to AA in both normal and ischemic brain, AA can reduce oxidized vitamin E and glutathione, other protectors of brain against damaging reactive oxygen species which build up in ischemic brain; (3) AA itself can protect brain against damaging reactive oxygen species; (4) AA is an essential cofactor for several enzymes in brain including ten-eleven translocase-2 which upregulates production of protective molecules like brain-derived neurotrophic factor; and (5) DHAA after conversion to AA prevents both lipid oxidation and presumably oxidation of other labile substances (e.g., dopamine) in ischemic brain. In terms of safety, based on all available animal information, DHAA is safe in the proposed dosing regimen. For human clinical trials, the methodology for conducting the proposed animal safety, clinical pharmacology and phase II efficacy studies is straightforward. Finally, if DHAA preserved brain substance and function in humans, it could be employed in pre-hospital stroke patients.
Asunto(s)
Ácido Ascórbico/metabolismo , Encéfalo/metabolismo , Ácido Deshidroascórbico/administración & dosificación , Ácido Deshidroascórbico/farmacocinética , Accidente Cerebrovascular/tratamiento farmacológico , Accidente Cerebrovascular/metabolismo , Animales , Encéfalo/efectos de los fármacos , Medicina Basada en la Evidencia , Humanos , Modelos Neurológicos , Resultado del Tratamiento , Vitaminas/administración & dosificación , Vitaminas/farmacocinéticaRESUMEN
Some investigations in Arterial Tortuosity Syndrome (ATS) suggest that impaired intracellular transport of the oxidized form of vitamin C (dehydroascorbic acid, DHAA) is at the core of the pathogenesis. Lack of vitamin C for lysyl- and prolyl-hydroxylase activity may explain the defects in collagen and elastin formation found in ATS, and draws strong parallels between ATS and scurvy. Topically applied vitamin C has a well-established basis in the field of skin care, and part of its benefit is attributed to proper collagen formation in the skin. The ATS studies suggest that DHAA transport is necessary for normal skin collagen formation, and this has implications as to the forms of vitamin C best-suited for topical skin care.
Asunto(s)
Arterias/anomalías , Colágeno/biosíntesis , Ácido Deshidroascórbico/metabolismo , Elastina/biosíntesis , Inestabilidad de la Articulación/metabolismo , Enfermedades Cutáneas Genéticas/metabolismo , Malformaciones Vasculares/metabolismo , Arterias/metabolismo , Transporte Biológico Activo , Ácido Deshidroascórbico/administración & dosificación , Proteínas Facilitadoras del Transporte de la Glucosa/genética , Proteínas Facilitadoras del Transporte de la Glucosa/metabolismo , Humanos , Inestabilidad de la Articulación/tratamiento farmacológico , Inestabilidad de la Articulación/etiología , Mutación , Cuidados de la Piel/métodos , Enfermedades Cutáneas Genéticas/tratamiento farmacológico , Enfermedades Cutáneas Genéticas/etiología , Malformaciones Vasculares/tratamiento farmacológico , Malformaciones Vasculares/etiologíaRESUMEN
Vitamin C deficiency globally affects several hundred million people and has been associated with increased morbidity and mortality in numerous studies. In this study, bioavailability of the oxidized form of vitamin C (l-dehydroascorbic acid or DHA)-commonly found in vitamin C containing food products prone to oxidation-was studied. Our aim was to compare tissue accumulation of vitamin C in guinea pigs receiving different oral doses of either ascorbate or DHA. In all tissues tested (plasma, liver, spleen, lung, adrenal glands, kidney, muscle, heart, and brain), only sporadic differences in vitamin C accumulation from ascorbate or DHA were observed except for the lowest dose of DHA (0.25mg/ml in the drinking water), where approximately half of the tissues had slightly yet significantly less vitamin C accumulation than from the ascorbate source. As these results contradicted data from rats, we continued to explore the ability to recycle DHA in blood, liver and intestine in guinea pigs, rats and mice. These investigations revealed that guinea pigs have similar recycling capacity in red blood cells as observed in humans, while rats and mice do not have near the same ability to reduce DHA in erythrocytes. In liver and intestinal homogenates, guinea pigs also showed a significantly higher ability to recycle DHA compared to rats and mice. These data demonstrate that DHA in guinea pigs-as in humans-is almost as effective as ascorbate as vitamin C source when it comes to taking up and storing vitamin C and further suggest that the guinea pig is superior to other rodents in modeling human vitamin C homeostasis.
Asunto(s)
Ácido Ascórbico/administración & dosificación , Ácido Deshidroascórbico/administración & dosificación , Intestinos/química , Hígado/química , Vitaminas/administración & dosificación , Animales , Ácido Ascórbico/farmacocinética , Deficiencia de Ácido Ascórbico/tratamiento farmacológico , Ácido Deshidroascórbico/farmacocinética , Suplementos Dietéticos , Relación Dosis-Respuesta a Droga , Eritrocitos/química , Cobayas , Humanos , Ratones , Ratas , Distribución Tisular , Vitaminas/farmacocinéticaRESUMEN
A porous scaffold was developed to support normal tissue regeneration in the presence of residual tumor disease. It was prepared by gelatin crosslinked with dehydroascorbic acid (DHA). A physicochemical characterization of the scaffold was carried out. SEM and mercury porosimetry revealed a high porosity and interconnection of pores in the scaffold. Enzymatic degradation provided 56% weight loss in ten days. The scaffold was also evaluated in vitro for its ability to support the growth of normal cells while hindering tumor cell development. For this purpose, primary human fibroblasts and osteosarcoma tumor cells (MG-63) were seeded on the scaffold. Fibroblasts attached the scaffold and proliferated, while the tumor cells, after an initial attachment and growth, failed to proliferate and progressively underwent cell death. This was attributed to the progressive release of DHA during the scaffold degradation and its cytotoxic activity towards tumor cells.
Asunto(s)
Antineoplásicos/química , Ácido Deshidroascórbico/química , Gelatina/química , Andamios del Tejido/química , Antineoplásicos/administración & dosificación , Materiales Biocompatibles/química , Adhesión Celular , Línea Celular Tumoral , Proliferación Celular , Supervivencia Celular , Células Cultivadas , Reactivos de Enlaces Cruzados , Ácido Deshidroascórbico/administración & dosificación , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Neoplasia Residual/tratamiento farmacológico , Neoplasia Residual/patología , Neoplasia Residual/cirugía , Regeneración , Ingeniería de TejidosRESUMEN
Thawed ram spermatozoa were incubated at 37°C in the presence of dehydroascorbic acid (DHA), TEMPOL (TPL), N-acetyl-cysteine (NAC) and rutin (RUT), at 0.1 and 1 mm, in order to test their effects on sperm physiology. Cryopreserved spermatozoa from four rams were thawed, pooled, washed and incubated in TALP-Hepes with 1 mm or 0.1 mm of each antioxidant, performing a replicate with induced oxidative stress (Fe(2+) /ascorbate). Motility (CASA), viability and mitochondrial membrane potential (flow cytometry) were analysed at 2 and 4 h. Lipoperoxidation (MDA production), intracellular reactive oxygen species (ROS) and DNA status (TUNEL) were analysed at 4 h. Antioxidants, except DHA 0.1 mm, decreased motility and kinematic parameters, but had little effect on viability or mitochondrial activity. Except 1 mm DHA, the antioxidants reduced ROS at 4 h. Moreover, NAC 1 mm, rutin and TEMPOL reduced ROS and DNA damage in the presence of oxidative stress. N-acetyl-cysteine, rutin 1 mm and TEMPOL reduced lipoperoxidation in the presence of oxidative stress. However, DHA did not affect lipoperoxidation. At 1 mm, DHA increased DNA damage in the absence of oxidative stress. Dehydroascorbic acid effects could arise from spermatozoa having a low capacity for reducing it to ascorbic acid, and it may be tested in the presence of other antioxidants or reducing power. Future research should focus in testing whether the inhibition of motility observed for NAC, rutin and TEMPOL is reversible. These antioxidants might be useful at lower temperatures (refrigerated storage or cryopreservation) when their protective effects could be advantageous.
Asunto(s)
Antioxidantes/farmacología , Preservación de Semen/veterinaria , Espermatozoides/efectos de los fármacos , Espermatozoides/fisiología , Acetilcisteína/administración & dosificación , Acetilcisteína/farmacología , Animales , Óxidos N-Cíclicos/administración & dosificación , Óxidos N-Cíclicos/farmacología , Daño del ADN/efectos de los fármacos , Ácido Deshidroascórbico/administración & dosificación , Ácido Deshidroascórbico/farmacología , Relación Dosis-Respuesta a Droga , Masculino , Preservación de Semen/métodos , Marcadores de Spin , Temperatura , Factores de TiempoRESUMEN
The aim of this study is to determine the protective effects of vitamin D(3) and dehydroascorbic acid (DHA), a blood-brain barrier transportable form of vitamin C, against ischemia/reperfusion (I/R) injury on a middle cerebral artery occlusion/reperfusion model of brain since reactive oxygen species play an important role in the pathophysiology of I/R injury in brain. In order to examine antioxidant status and lipid peroxidation, we assayed malondialdehyde (MDA) levels as a marker of lipid peroxidation, and reduced glutathione (GSH) and superoxide dismutase (SOD) enzyme activities as free radical scavenging enzymes in cortex and corpus striatum (CS). Wistar albino rats were divided into five equal groups of each consisting of seven rats: control, I/R, I/R + DHA, I/R + vitamin D(3), and I/R + vitamin D(3) + dehydroascorbic acid groups. MDA levels were found to be increased in the I/R group, I/R + DHA, and I/R + vitamin D(3) groups compared with the control group in both cortex and corpus striatum. However, MDA level were found to be significantly decreased in only I/R + vitamin D(3) + DHA group compared with the I/R group in cortex (P < 0.0001). MDA levels were not significantly different in I/R + DHA, and I/R + vitamin D(3) groups compared with the I/R group. GSH and SOD enzyme activities were significantly decreased in I/R, I/R + DHA, and I/R + vitamin D(3) groups compared with the control group in both cortex and corpus striatum (CS) (P < 0.0001). Whereas, both GSH and SOD activity were increased in I/R + vitamin D(3) + DHA group compared with the I/R group in both cortex and CS (P < 0.001 in cortex, P < 0.001 in CS for SOD P < 0.002 in cortex P < 0.03 in CS for GSH). Our results demonstrate that the combination of vitamin D(3) and DHA treatment prevent free radical production and dietary supplementation of vitamin D(3) and DHA which may be useful in the ischemic cerebral vascular diseases.
Asunto(s)
Isquemia Encefálica/tratamiento farmacológico , Colecalciferol/administración & dosificación , Ácido Deshidroascórbico/administración & dosificación , Fármacos Neuroprotectores/administración & dosificación , Daño por Reperfusión/prevención & control , Análisis de Varianza , Animales , Isquemia Encefálica/metabolismo , Corteza Cerebral/metabolismo , Colecalciferol/uso terapéutico , Cuerpo Estriado/metabolismo , Ácido Deshidroascórbico/uso terapéutico , Modelos Animales de Enfermedad , Combinación de Medicamentos , Glutatión/metabolismo , Masculino , Malondialdehído/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Especies Reactivas de Oxígeno/metabolismo , Daño por Reperfusión/metabolismo , Superóxido Dismutasa/metabolismoRESUMEN
Ascorbate (AA), an antioxidant substance known as vitamin C, exists in the brain at a high concentration, although transfer into the brain after systemic administration of AA itself is limited. Intraperitoneal administration of dehydroascorbate (DHA) resulted in a rapid and progressive increase in extracellular AA in rat striatum in a dose-dependent manner. DHA administration increased 2,3- and 2,5-dihydroxybenzoate (2,3- and 2,5-DHBA) formation from salicylate in parallel with the increase in extracellular AA. Intrastriatal administration of active AA oxidase (AAO), but not the inactivated enzyme, completely suppressed the increase in 2,3- and 2,5-DHBA formation after the DHA administration. These findings suggest that extracellular AA might stimulate hydroxyl radical (OH) generation in the striatum. This is supported by the observation of dose-dependent OH generation upon intrastriatal administration of AA itself. In addition, deferoxamine, an iron chelator, decreased basal 2,3- and 2,5-DHBA formation and strongly, though not completely, suppressed the DHA-induced increase of 2,3- and 2,5-DHBA formation. Therefore, increased extracellular AA might function as a prooxidant and stimulate OH generation in cooperation with iron in rat striatum.
Asunto(s)
Ácido Ascórbico/efectos adversos , Cuerpo Estriado/efectos de los fármacos , Espacio Extracelular/metabolismo , Radical Hidroxilo/metabolismo , Animales , Ácido Ascórbico/administración & dosificación , Ácido Ascórbico/farmacocinética , Conducta Animal/efectos de los fármacos , Cuerpo Estriado/metabolismo , Ácido Deshidroascórbico/administración & dosificación , Ácido Deshidroascórbico/efectos adversos , Ácido Deshidroascórbico/farmacocinética , Gentisatos/metabolismo , Hidroxibenzoatos/metabolismo , Masculino , Microdiálisis , Ratas , Ratas Sprague-DawleyRESUMEN
We performed oral loading of AsA or DAsA (1 mmol) in subjects who had consumed a diet low in vitamin C (C) (C< or =5 mg/d) for 3 d before loading, and measured urinary and blood vitamin C. Since the crossover method was used, the same experiment was repeated after an interval of about 1 mo in each subject. The results of the experiment including a total of 17 subjects for 2005 and 2006, were as follows. (1) There were marked individual differences in urinary C excretion. (2) The C level in 24-h urine after C loading did not differ between the two orally administered C forms (AsA and DAsA). (3) C excretion between 0 and 3 h after C loading was significantly higher (p<0.05) for the DAsA group, while those between 3 and 6, 6 and 9, 9 and 12, and 12 and 24 h after C loading were significantly higher (p<0.05 or p<0.01) for the AsA group. (4) The blood C concentration and the increase in C 1 h after C loading were significantly higher (p<0.05 and p<0.01, respectively) in the DAsA than in the AsA group. (5) Evaluation of the association between C metabolism and the single nucleotide polymorphisms of glutathione S-transferase P (GSTP) 1-1 showed a lower urinary C excretion and a significantly lower C level in 24-h urine (p<0.05) after AsA loading, and a significantly lower urinary C excretion between 0 and 3 h after DAsA loading (p<0.05) for the GA heterozygotes than for the AA homozygotes. Considering the activity of C as DAsA in humans, based on urinary and blood C levels after a single loading of C, the utilization of DAsA is equivalent to that of AsA, although the metabolic turnover time is different. The involvement of polymorphisms in the xenobiotic metabolizing enzyme, GSTP1-1, in C metabolism, particularly urinary C excretion, was also clarified. This demonstrates the necessity of considering gene polymorphisms in determining individual C requirements. An abstract of this paper was reported by the Vitamin C Research Committee (Ochanomizu University) in 2007.
Asunto(s)
Ácido Ascórbico/sangre , Ácido Ascórbico/orina , Ácido Deshidroascórbico , Vitaminas , Administración Oral , Estudios Cruzados , Ácido Deshidroascórbico/administración & dosificación , Ácido Deshidroascórbico/sangre , Ácido Deshidroascórbico/orina , Femenino , Humanos , Vitaminas/administración & dosificación , Vitaminas/sangre , Vitaminas/orina , Adulto JovenRESUMEN
Ascorbic acid (AA) and dehydroascorbic acid (DHA) have been shown to have protective effects as anti-oxidants in experimental neurological disorder models such as stroke, ischemia, and epileptic seizures. The present study was conducted to examine the protective effects of AA and DHA on kainic acid (KA) neurotoxicity using organotypic hippocampal slice cultures. After 12h KA treatment, significant delayed neuronal death was detected in the CA3, but not the CA1, region. Pretreatment with intermediate doses of AA and DHA significantly prevented cell death and inhibited reactive oxygen species (ROS) level, and mitochondrial dysfunction in the CA3 region. In contrast, pretreatment with low or high doses of AA or DHA was not effective. These data suggest that pretreatment with both AA and DHA has dose-dependent neuroprotective effects on KA-induced neuronal injury through inhibiting ROS generation and mitochondrial dysfunction.
Asunto(s)
Ácido Ascórbico/administración & dosificación , Hipocampo/citología , Hipocampo/metabolismo , Neuronas/citología , Neuronas/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Animales , Antioxidantes/administración & dosificación , Apoptosis/efectos de los fármacos , Ácido Deshidroascórbico/administración & dosificación , Relación Dosis-Respuesta a Droga , Hipocampo/efectos de los fármacos , Técnicas In Vitro , Neuronas/efectos de los fármacos , Ratas , Ratas Sprague-DawleyRESUMEN
Vitamin C (ASC) is well known as an outstanding antioxidant in animal tissues. This concept is reviewed from a chemical standpoint, starting from a chemical view of radical reactions in the cell. ASC, vitamin E, and lipid hydroperoxide were selected as key molecules involved in radical reactions in the cell, and their efficiencies as an index of oxidative stress were evaluated. At first, methods for specific and sensitive determination of ASC and lipid hydroperoxide were developed. Based on comparisons of these indices during oxidative stress in typical pathological conditions, such as diabetes and liver damage by toxicants, ASC concentration was found to be the most sensitive index in animal tissues. Antioxidative effect of food factors in vivo can be evaluated on the basis of these indices. Analysis of oxidation of low-density lipoprotein (LDL) revealed that degradation and cross-link of apolipoprotein B-100 (apoB) are extremely facile processes. Fragmented and conjugated apoB proteins are present in normal human serum, and tend to increase with age based on immunoblot analysis. Estimation of these products allows us a mechanism-based diagnosis of atherosclerosis. A significant relationship between plasma ASC level and the sum of these apoB products was found. In conclusion, specifically determined ASC concentration sensitively reflects oxidative stress in tissues.
Asunto(s)
Ácido Ascórbico/metabolismo , Ácido Ascórbico/fisiología , Estrés Oxidativo/fisiología , Animales , Apoptosis/fisiología , Arteriosclerosis/metabolismo , Arteriosclerosis/prevención & control , Ácido Ascórbico/química , Deficiencia de Ácido Ascórbico/metabolismo , Ácido Deshidroascórbico/administración & dosificación , Alimentos , Humanos , Técnicas In Vitro , Peróxidos Lipídicos/fisiología , Ratones , Estructura Molecular , Especificidad de Órganos , Ratas , Especies Reactivas de Oxígeno/metabolismo , Vitamina E/fisiologíaRESUMEN
The biological activity of L-dehydroascorbic acid (DHA), which is easily formed from L-ascorbic acid (ASC) during storage and cooking processes, has been considered to be equivalent to that of ASC on the basis of studies made several decades ago, when a specific method to determine ASC was not available. The nutritional activity of orally ingested DHA has now been evaluated by comparing ASC concentrations in 12 tissues of rats administered four different doses of ASC. Determinations were made by using the specific and sensitive method, which had been developed by us. Here it is shown that the efficiency of DHA was almost 10% of that of ASC on a molar basis, based on animal experiments using the inherently scorbutic ODS rat, which is a convenient human model animal to investigate the metabolism of vitamin C. On the basis of these findings, it is proposed that it is necessary to reevaluate the nutritional requirement of vitamin C based on both ASC and DHA contents of foods.
Asunto(s)
Ácido Ascórbico/análisis , Ácido Deshidroascórbico/farmacocinética , Escorbuto/tratamiento farmacológico , Administración Oral , Animales , Ácido Deshidroascórbico/administración & dosificación , Modelos Animales de Enfermedad , Masculino , Necesidades Nutricionales , Valor Nutritivo , Ratas , Distribución TisularRESUMEN
BACKGROUND: Reactive oxygen species generated by ultraviolet light result in photocarcinogenic and photoaging changes in the skin. Antioxidants protect skin from these insults. OBJECTIVE: This study defines formulation characteristics for delivering L-ascorbic acid into the skin to supplement the skin's natural antioxidant reservoir. METHODS: L-ascorbic acid or its derivatives were applied to pig skin. Skin levels of L-ascorbic acid were measured to determine percutaneous delivery. RESULTS: L-ascorbic acid must be formulated at pH levels less than 3.5 to enter the skin. Maximal concentration for optimal percutaneous absorption was 20%. Tissue levels were saturated after three daily applications; the half-life of tissue disappearance was about 4 days. Derivatives of ascorbic acid including magnesium ascorbyl phosphate, ascorbyl-6-palmitate, and dehydroascorbic acid did not increase skin levels of L-ascorbic acid. CONCLUSIONS: Delivery of topical L-ascorbic acid into the skin is critically dependent on formulation characteristics.
Asunto(s)
Antioxidantes/administración & dosificación , Antioxidantes/farmacocinética , Ácido Ascórbico/administración & dosificación , Ácido Ascórbico/farmacocinética , Absorción Cutánea , Protectores Solares/administración & dosificación , Protectores Solares/farmacocinética , Administración Cutánea , Animales , Ácido Ascórbico/análogos & derivados , Ácido Deshidroascórbico/administración & dosificación , Ácido Deshidroascórbico/farmacocinética , Concentración de Iones de Hidrógeno , Piel/metabolismo , PorcinosRESUMEN
Ascorbate (AH, the reduced form of vitamin C) is an important radical scavenger and antioxidant in human plasma; the resulting ascorbyl radical can disproportionate to AH and dehydroascorbic acid (DHA). Here we address potential maintenance mechanism(s) for extracellular AH by examining the ability of cells to convert extracellularly presented DHA to AH. DHA was rapidly transported into human liver (HepG2), endothelial and whole blood cells in vitro by plasma membrane glucose transporters and reduced intracellularly. Liver cells displayed the highest capacity to release the intracellularly accumulated AH. The proteins responsible for DHA uptake and AH release could be distinguished by inhibitor studies. Thus, unlike DHA uptake, AH efflux was largely insensitive to cytochalasin B and thiol-reactive agents but was inhibited by phloretin, 4,4'-di-isothiocyanostilbene-2,2'-disulphonate and isoascorbate. Efflux of AH from cells was temperature-sensitive and saturable with a low affinity (millimolar, intracellular) for AH. In addition to isolated liver cells, perfusion of intact rat and guinea-pig liver with DHA resulted in AH in the circulating perfusate. Our results show that hepatocytes take up and reduce DHA and subsequently release part of the AH formed, probably via a membrane transporter. By converting extracellular DHA to extracellular AH, the liver might contribute to the maintenance of plasma AH, a process that could be important under conditions of oxidative stress.
Asunto(s)
Ácido Ascórbico/sangre , Ácido Ascórbico/metabolismo , Ácido Deshidroascórbico/metabolismo , Hígado/metabolismo , Animales , Transporte Biológico , Células Sanguíneas/metabolismo , Línea Celular , Ácido Deshidroascórbico/administración & dosificación , Transporte de Electrón , Cobayas , Humanos , Técnicas In Vitro , Cinética , Hígado/citología , Masculino , Modelos Biológicos , Proteínas de Transporte de Monosacáridos/metabolismo , Oxidación-Reducción , Ratas , Ratas Wistar , TemperaturaRESUMEN
The integration of proteolytic pathways with metabolism was investigated in perfused rat myocardium. After a 10-min incorporation period, the minute-to-minute release of [3H]leucine from myocardial proteins was measured in nonrecirculating effluent perfusate. The nontoxic pro-oxidant probe diamide (100 microM) or a supraphysiological concentration of the endogenous oxidative metabolite dehydroascorbic acid (200 microM) reversibly inhibited 75% of myocardial proteolysis consisting of several known subcomponents (redox dependent); however, 25% of proteolysis was diamide insensitive (redox independent). Decrease in extracellular glucose concentration from 10 to 0.1 mM strongly increased the potencies of minimally effective concentrations of diamide (10 microM) or dehydroascorbic acid (15 microM) by approximately 10-fold to the respective potencies maximally inhibiting proteolysis. The reversal of diamide action was also strongly dependent on the perfusate glucose concentration observed at 0.1, 0.2, 1.0 and 10 mM glucose. Proteolytic inhibition caused by diamide (100 microM) was not accompanied by change in basal tissue ATP content of 5 micromol/g wet wt. Conversely, nearly lethal 60% ATP depletion caused by sodium azide (0.4 mM) was not accompanied by change in total [3H]leucine release. Results indicate that a large proteolytic subcomponent (75%) is maintained by redox chains fed by glucose; however, there is no apparent linkage of this proteolysis to short-term ATP fluctuations. A distinct major proteolytic subcomponent (25%) does not vary in response to experimental intervention in either ATP content or redox chains.
Asunto(s)
Proteínas Musculares/metabolismo , Miocardio/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Ácido Deshidroascórbico/administración & dosificación , Ácido Deshidroascórbico/farmacología , Diamida/farmacología , Endopeptidasas/metabolismo , Glucosa/administración & dosificación , Glucosa/farmacología , Leucina/metabolismo , Oxidantes/farmacología , Oxidación-Reducción , Perfusión , Inhibidores de Proteasas/farmacología , Ratas , Azida Sódica/farmacología , TritioRESUMEN
In our previous paper (Biochim. Biophys. Acta 1379 (1998) 257-263), we demonstrated that bicarbonate promotes a cleavage of lactone ring of dehydroascorbate (DHA) on the basis of in vitro experiments. In the present study, we examined the degradation of DHA in blood circulation in vivo by using a high-performance liquid chromatographic method for the determination of ascorbate (AsA), DHA and 2,3-diketogulonate (2,3-DKG), which required no pretreatment of biological fluids. When DHA was intravenously administered to rats, a rapid disappearance of DHA (t1/2 < 1 min) and a concomitant appearance of 2,3-DKG in blood circulation were observed. Approximately 90% of the administered DHA were excreted into urine as resulting 2,3-DKG (55%) and AsA (31%), respectively. Furthermore, we elucidated that rat plasma lacks an enzyme having an aldonolactonase-like activity. The result of the present study suggests that this DHA disappearance is a function of both a chemical degradation to 2,3-DKG and a reduction to AsA.
Asunto(s)
Ácido 2,3-Dicetogulónico/sangre , Ácido Deshidroascórbico/sangre , Animales , Ácido Ascórbico/sangre , Ácido Ascórbico/orina , Hidrolasas de Éster Carboxílico/sangre , Cromatografía Líquida de Alta Presión , Ácido Deshidroascórbico/administración & dosificación , Productos Finales de Glicación Avanzada/metabolismo , Inyecciones Intravenosas , Cinética , Masculino , Oxidación-Reducción , Estrés Oxidativo , Ratas , Ratas WistarRESUMEN
The tissue distribution of L-ascorbic acid (AsA) and dehydro-L-ascorbic acid (DAsA) in guinea pigs injected with DAsA intravenously was examined using high-performance liquid chromatography. DAsA injected into guinea pigs fed normal diets containing AsA (control group) was readily taken into erythrocytes, and AsA contents of plasma and other tissues rapidly increased after DAsA injection. In animals fed vitamin C-deficient diets, DAsA was also detected in erythrocytes; however, the increase of AsA in their tissues was considerably less than that of control group. From these results, it was suggested that utilization of DAsA as AsA in vitamin C-deficient guinea pigs was less than that of control animals, and the reduction mechanism of DAsA to AsA in vitamin C-deficient guinea pigs may have differed from that of control groups.
Asunto(s)
Deficiencia de Ácido Ascórbico/metabolismo , Ácido Ascórbico/análogos & derivados , Ácido Ascórbico/análisis , Ácido Deshidroascórbico/análisis , Administración Oral , Animales , Ácido Ascórbico/biosíntesis , Cromatografía Líquida de Alta Presión , Ácido Deshidroascórbico/administración & dosificación , Cobayas , Inyecciones Intravenosas , Masculino , Distribución TisularRESUMEN
The present study was designed to test the effect of a combination of dehydroascorbic acid (DHA) and hydroxycobalamin (vitamin B12) on the survival of mice bearing L1210 leukemia. Results showed a significant increase in survival of treated mice compared with controls (p less than or equal to 0.0001) (Student's t-test). This positive effect was significantly lost when DHA was substituted by ascorbic acid (AA) in the same experimental conditions. In vitro findings also revealed that the DHA-B12 combination specifically inhibited mitoses of L1210 cells while non-neoplastic L929 cells were not affected.