RESUMEN

BACKGROUND: The precise mechanisms regulating the natriuretic peptide urodilatin (ANP-95-126) remain to be defined. Renal excretion of urodilatin (U(URO)V) has been shown to be modified by variations in plasma sodium and renal perfusion pressure. This suggests a relationship between urodilatin and the renin-angiotensin system. METHODS: We investigated the effects of angiotensin II (AII, 0.1 nmol/l) and the AT(1) receptor antagonist losartan (LS, 1 micromol/l) on U(URO)V and renal function in isolated rat kidneys perfused for 180 min in a closed circuit system. A further series employing a vasoconstricting concentration of endothelin-1 (ET-1, 0.01 nmol/l) was performed to explore the effects of vasoconstriction and glomerular filtration rate (GFR) on U(URO)V. RESULTS: Urine flow (UV) and urinary sodium excretion (U(Na)V) decreased and renal vascular resistance (RVR) increased after treatment with AII (n = 5) in comparison with a control group (n = 6; p < 0.05). Treatment with LS (n = 5) and AII+LS (n = 5) had no significant effect on these parameters. GFR decreased after AII (p < 0.05) and was not significantly altered by other interventions. U(URO)V decreased after AII (p < 0.05) and was comparable to the control group after LS and AII+LS. ET-1 (n = 5) induced a significant increase in RVR and decreased UV and U(Na)V (p < 0.05). Point-to-point analysis revealed that the ET-1-induced vasoconstriction and the subsequent decrease in GFR had no effect on U(URO)V. CONCLUSIONS: This suggests that vasoconstrictory concentrations of AII decrease U(URO)V in the isolated perfused rat kidney. The lack of effect of ET-1 on U(URO)V suggests that the AII-induced alterations in urodilatin excretion cannot be explained by vasoconstriction per se.

Asunto(s)

Angiotensina II/farmacología , Antagonistas de Receptores de Angiotensina , Factor Natriurético Atrial/orina , Riñón/efectos de los fármacos , Losartán/farmacología , Fragmentos de Péptidos/orina , Animales , Endotelina-1/farmacología , Tasa de Filtración Glomerular/efectos de los fármacos , Riñón/metabolismo , Masculino , Perfusión , Ratas , Ratas Sprague-Dawley , Receptor de Angiotensina Tipo 1 , Receptor de Angiotensina Tipo 2 , Circulación Renal/efectos de los fármacos , Sodio/metabolismo , Resistencia Vascular/efectos de los fármacos , Vasoconstricción/efectos de los fármacos , Vasoconstrictores/farmacología

RESUMEN

AIMS: To determine whether a coupling of plasma atrial natriuretic peptide (ANP) and renal excretion of urodilatin (U(URO)V)--recently observed during supraphysiological concentrations of ANP--may also be detected during moderate changes in ANP levels, i.e. if ANP is increased by supine positioning and decreased by applying continuous positive airway pressure (CPAP). MATERIAL AND METHODS: We investigated 10 healthy male volunteers, orally hydrated with 200 ml water/h, in a randomized crossover study for periods of 1 hour following 2 protocols. Protocol 1: sitting and supine position. Protocol 2: sitting with and without a CPAP of 8 cm H2O. RESULTS: ANP increased ongoing from the sitting to the supine position (SIT-1: 13.2 +/- 4.7; SUP: 27.9 +/- 21.9 pg x ml(-1); p < 0.01) during protocol 1 and decreased after the onset of CPAP in seated subjects (SIT-2: 16.9 +/- 7.9; SIT-CPAP: 13.9 +/- 6.5 pg x ml(-1); p < 0.05) during protocol 2. U(URO)V decreased slightly, but not significantly, during protocol I (SIT-1: 63.9 +/- 21.7; SUP: 49.9 +/- 13.2 fmol x min(-1)) and remained unchanged after institution of CPAP in the sitting position (SIT-2: 68.5 +/- 25.2; SIT-CPAP: 68.5 +/- 50.2 fmol x min(-1)). Correlation analysis revealed no relationship between plasma ANP and U(URO)V. CONCLUSIONS: Moderate variations in the levels of ANP in water-loaded volunteers do not induce parallel changes in the urinary excretion of urodilatin.

Asunto(s)

Factor Natriurético Atrial/sangre , Factor Natriurético Atrial/metabolismo , Riñón/irrigación sanguínea , Riñón/fisiología , Fragmentos de Péptidos/metabolismo , Respiración con Presión Positiva , Postura/fisiología , Adulto , Hemodinámica/fisiología , Humanos , Masculino , Natriuresis/fisiología , Valores de Referencia , Estadística como Asunto

RESUMEN

BACKGROUND: To evaluate the effectiveness of a bolus application of pentoxifylline (PTXF) at the beginning of CPR in a standardized resuscitation animal model. METHODS AND RESULTS: In a laboratory model of cardiac arrest, 12 Wistar rats (382-413 g) were randomized into two groups. Both groups underwent 4 min of cardiopulmonary arrest induced by a transthoracic application of a fibrillating current of 10 mA. At the beginning of CPR, group one (n=6) received a bolus injection of 10 mg kg(-1) body weight PTXF versus sodium chloride in group two (controls: n=6). All animals developed a severe lactate acidosis during and after CPR but in PTXF treated animals acid-base values returned to baseline pattern. During return of spontaneous circulation (ROSC) in the PTXF group lactate concentration decreased from 13.4+/-2.1 to 1.9+/-0.7 mmol l(-1) within 60 min (P<0.01). In control animals, lactate values remained high (10.8+/-3.5 by 60 min, P<0.01). After bolus injection of PTXF pH increased from 6.93+/-0.06 to 7.29+/-0.13 within 60 min of ROSC versus 6.85+/-0.05 to 6.97+/-0.23 in sodium chloride treated animals (P<0.01). Within 5 min of ROSC, PTXF treated animals achieved higher oxygenation values (PTXF P(a)O(2)=216.9+/-62.5 mmHg, control 132. 2+/-15.1 mmHg, P<0.01). CONCLUSIONS: Administration of PTXF at the beginning of CPR improved macrocirculation, acid-base status and arterial oxygenation.

Asunto(s)

Acidosis Láctica/sangre , Acidosis Láctica/tratamiento farmacológico , Reanimación Cardiopulmonar/métodos , Paro Cardíaco/sangre , Paro Cardíaco/tratamiento farmacológico , Pentoxifilina/uso terapéutico , Vasodilatadores/uso terapéutico , Desequilibrio Ácido-Base/sangre , Desequilibrio Ácido-Base/tratamiento farmacológico , Animales , Hemodinámica/efectos de los fármacos , Masculino , Distribución Aleatoria , Ratas , Ratas Wistar , Fibrilación Ventricular/tratamiento farmacológico

RESUMEN

BACKGROUND: The development of acute renal failure (ARF) significantly enhances the mortality of patients with Gram-negative septic shock. The role of specific bacterial virulence factors different from lipopolysaccharides (LPS) in the deterioration of renal function in septic shock remains to be determined. METHODS: An Escherichia coli wild-type strain (536/21 WT, O6:K15:H31) was isolated from a patient suffering from a urinary tract infection. The strain expresses various virulence factors (e.g. hemolysin, fimbriae) genetically encoded by pathogenicity islands. The spontaneous deletion mutant 536/21 Del lacks the expression of these virulence factors. Isolated rat kidneys were perfused with a suspension (5 x 10(4)/ml) of the respective strain or control perfusion medium and the renal functional parameters were analyzed. Intrarenal deposition of E. coli was detected by immunohistology and Gram staining. RESULTS: The perfusion of the isolated perfused rat kidney with a uropathogenic E. coli wild-type strain (536/21 WT) caused an acute deterioration of renal function which was not observed in kidneys exposed to a deletion mutant of E. coli 536/21 lacking the expression of virulence factors. The glomerular filtration rate and the urine flow rate significantly decreased only in kidneys perfused with the E. coli wild-type strain, while there was no change versus controls in kidneys perfused with the deletion mutant. CONCLUSIONS: Distinctive bacterial virulence factors different from LPS such as hemolysin and the presence of different fimbriae may contribute to the development of ARF in sepsis induced by E. coli. Anti-LPS strategies may not be sufficient to reduce the risk of ARF in Gram-negative septic shock.

Asunto(s)

Lesión Renal Aguda/microbiología , Escherichia coli/patogenicidad , Lesión Renal Aguda/fisiopatología , Animales , Adhesión Bacteriana , Velocidad del Flujo Sanguíneo , Endotelio Vascular/microbiología , Escherichia coli/genética , Escherichia coli/aislamiento & purificación , Tasa de Filtración Glomerular , Humanos , Riñón/irrigación sanguínea , Riñón/química , Riñón/microbiología , Lipopolisacáridos/análisis , Masculino , Mutación , Ratas , Ratas Sprague-Dawley , Infecciones Urinarias/microbiología , Resistencia Vascular , Virulencia

RESUMEN

BACKGROUND: This study aimed to characterise the composition of the pre-ocular fluid after transplantation of the autologous submandibular gland (SMG) for patients with severe dry eye. METHODS: Stimulated and unstimulated pre-ocular fluid from 15 patients (17 eyes) with a viable SMG graft ("SMG-salivary tears"), as well as normal tears and SMG saliva (20 normal subjects/ 20 eyes), was sampled. As global tear parameters, fern pattern analysis and SDS gel electrophoresis were performed. As specific quality parameters, total protein content, secretory immunoglobulin A (SIgA), lysozyme, amylase, sodium, potassium and osmolality were measured using routine laboratory methods. The flow rate of SMG-salivary tears was determined in 5 patients by means of sequential scintillography. RESULTS: The fern pattern of SMG-salivary tears was coarse and thus more similar to normal SMG saliva than tears. SDS gel electrophoresis of the SMG-salivary tears showed albumin and two unidentified proteins in addition to the normal tear pattern. Osmolality and total protein content of SMG-salivary tears were higher than in normal SMG saliva, but still lower than in normal tears. High activities of normal tear antibacterial proteins (SIgA, lysozyme and amylase) were detected in the salivary tears. Stimulation of the secretion did not alter the composition of SMG-salivary tears. The flow rate of SMG-salivary tears was closer to that of normal tears than normal SMG saliva. CONCLUSION: Salivary tears resulting from SMG-transplantation represent condensed SMG saliva. Thus their quality is intermediate between normal tears and normal SMG saliva. High levels of secretory proteins demonstrate that the gland maintains an active function. Surgical denervation and residual tear components from the ocular surface are the most likely factors to cause the complex differences between normal SMG saliva and SMG-salivary tears. The effects of this secretion on the ocular surface are currently being evaluated in a clinical and laboratory study.

Asunto(s)

Síndromes de Ojo Seco/cirugía , Glándula Submandibular/trasplante , Lágrimas/química , Adolescente , Adulto , Anciano , Amilasas/análisis , Síndromes de Ojo Seco/metabolismo , Femenino , Humanos , Inmunoglobulina A Secretora/análisis , Masculino , Persona de Mediana Edad , Muramidasa/análisis , Concentración Osmolar , Potasio/análisis , Proteínas/análisis , Cintigrafía , Sodio/análisis , Glándula Submandibular/diagnóstico por imagen , Glándula Submandibular/metabolismo , Lágrimas/metabolismo , Trasplante Autólogo , Resultado del Tratamiento

RESUMEN

The findings about mechanisms regulating production and excretion of urodilatin [ANP-(95-126)], a member of the atrial natriuretic peptide (ANP) family, are controversial. To elucidate a possible relationship between arterial blood pressure and renal urodilatin excretion, we studied the effects of different perfusion pressures on urine flow (UV), urinary sodium (U(Na)V), urinary potassium (U(K)V), and urodilatin excretion (U(URO)V), and the concentration of urodilatin in the perfusate (P(URO)) of isolated perfused rat kidneys. Kidneys were perfused for 180 min with constant perfusion pressures (80 and 120 mmHg, respectively; each, n = 4) in a closed circuit system. Samples of urine and perfusate were taken every 30 min. Mean UV, U(Na)V, U(K)V, and U(URO)V values were significantly higher with a perfusion pressure of 120 mmHg than with 80 mmHg, whereas P(URO) did not change significantly. Serial measurements revealed no direct relation of U(URO)V with either U(Na)V or UV. This suggests that renal perfusion pressure is a determinant of U(URO)V and that urinary and venous effluent concentrations of urodilatin (probably production) are not coupled directly and that U(URO)V and U(Na)V may dissociate during acute variations of sodium excretion and UV.

Asunto(s)

Factor Natriurético Atrial/orina , Presión Sanguínea/fisiología , Riñón/fisiología , Natriuresis/fisiología , Fragmentos de Péptidos/orina , Animales , Riñón/irrigación sanguínea , Masculino , Perfusión , Ratas , Ratas Sprague-Dawley

RESUMEN

BACKGROUND: This study aimed to characterise the composition of the pre-ocular fluid after transplantation of the autologous submandibular gland (SMG) for patients with severe dry eye. METHODS: Stimulated and unstimulated pre-ocular fluid from 15 patients (17 eyes) with a viable SMG graft ("SMG-salivary tears"), as well as normal tears and SMG saliva (20 normal subjects/20 eyes), was sampled. As global tear parameters, fern pattern analysis and SDS gel electrophoresis were performed. As specific quality parameters, total protein content, secretory immunoglobulin A (SIgA), lysozyme, amylase, sodium, potassium and osmolality were measured using routine laboratory methods. The flow rate of SMG-salivary tears was determined in 5 patients by means of sequential scintillography. RESULTS: The fern pattern of SMG-salivary tears was coarse and thus more similar to normal SMG saliva than tears. SDS gel electrophoresis of the SMG-salivary tears showed albumin and two unidentified proteins in addition to the normal tear pattern. Osmolality and total protein content of SMG-salivary tears were higher than in normal SMG saliva, but still lower than in normal tears. High activities of normal tear antibacterial proteins (SIgA, lysozyme and amylase) were detected in the salivary tears. Stimulation of the secretion did not alter the composition of SMG-salivary tears. The flow rate of SMG-salivary tears was closer to that of normal tears than normal SMG saliva. CONCLUSION: Salivary tears resulting from SMG-transplantation represent condensed SMG saliva. Thus their quality is intermediate between normal tears and normal SMG saliva. High levels of secretory proteins demonstrate that the gland maintains an active function. Surgical denervation and residual tear components from the ocular surface are the most likely factors to cause the complex differences between normal SMG saliva and SMG-salivary tears. The effects of this secretion on the ocular surface are currently being evaluated in a clinical and laboratory study.

Asunto(s)

Síndromes de Ojo Seco/cirugía , Saliva/metabolismo , Glándula Submandibular/trasplante , Lágrimas/metabolismo , Adolescente , Adulto , Anciano , Amilasas/metabolismo , Electroforesis en Gel de Poliacrilamida , Femenino , Humanos , Inmunoglobulina A Secretora/metabolismo , Masculino , Persona de Mediana Edad , Muramidasa/metabolismo , Concentración Osmolar , Potasio/metabolismo , Sodio/metabolismo , Glándula Submandibular/metabolismo , Trasplante Autólogo

RESUMEN

Activation of the human cellular immune system is associated with greatly increased formation of the pteridines neopterin and 7,8-dihydroneopterin. It has been postulated that pteridines play a role in the pathogenesis of the anaemia of inflammation. Herein, we studied effects of pteridines on renal function, primarily on the synthesis of erythropoietin (Epo). The experiments were performed with isolated rat kidneys which were perfused hypoxically (pO2 26 mmHg) at constant pressure (100 mmHg) in a serum-free recirculation system for 3 h. The results show that the rate of the production of Epo was significantly lowered when neopterin or 7,8-dihydroneopterin were added to the perfusate. Neopterin (200 microM) also reduced the renal Epo mRNA level. Both pteridines increased renal vascular resistance. 7,8-Dihydroneopterin lowered urine flow and glomerular filtration rate more potently than neopterin. Renal O2 consumption and parameters of exocrine renal function (fractional reabsorption rates of sodium, glucose and water) were not altered by the pteridines, while the glomerular permeability was greatly increased. These results suggest that activated macrophages may not only inhibit the synthesis of Epo by generating cytokines and reactive O2 species but also by the release of pteridines. In vivo, high concentrations of pteridines in renal tissue may aggravate the anaemia of inflammation.

Asunto(s)

Antioxidantes/farmacología , Eritropoyetina/biosíntesis , Riñón/metabolismo , Neopterin/farmacología , Pteridinas/farmacología , Animales , Hipoxia de la Célula , Ensayo de Inmunoadsorción Enzimática , Humanos , Riñón/efectos de los fármacos , Riñón/fisiopatología , Masculino , Reacción en Cadena de la Polimerasa , ARN Mensajero/biosíntesis , Ratas , Ratas Sprague-Dawley

RESUMEN

The most important stimulus for the enhanced synthesis of erythropoietin (Epo) is a lowered O2 tension in the tissue. However, the mechanism by which an impaired O2 supply is transduced into appropriate Epo production is still not fully understood. Recently, studies in human hepatoma cells (line HepG2) indicate that reactive O2 species are involved in the signal transduction from the cellular O2 sensor to the Epo gene. To clarify the role of reactive O2 species in the regulation of Epo synthesis in the kidney, the principal Epo-producing organ in vivo, we investigated the influence of potent pro- and antioxidants on Epo production in isolated perfused rat kidneys. Under normoxic conditions, the iron chelator desferrioxamine and the antioxidant vitamin A increased renal Epo production, mimicking hypoxic induction. In contrast, supplementation of the perfusion medium of hypoxically perfused kidneys with the prooxidant compounds H2O2 or pyrogallol caused a significant reduction of Epo synthesis. The inhibition of Epo formation by reactive O2 species could be completely antagonized by desferrioxamine and the hydroxyl radical-(OH*)-scavenger tetramethylthiourea. Vitamin A also antagonized the H2O2-dependent inhibition of hypoxically induced Epo synthesis. Interestingly, the addition of the antioxidant vitamin A to hypoxically perfused kidneys also induced Epo production significantly. Our data strongly support the idea that reactive O2 species, especially H2O2, are part of the signaling chain of the cellular O2-sensing mechanism regulating the renal synthesis of Epo.

Asunto(s)

Antioxidantes/farmacología , Eritropoyetina/biosíntesis , Riñón/metabolismo , Oxidantes/farmacología , Animales , Quelantes/farmacología , Deferoxamina/farmacología , Eritropoyetina/antagonistas & inhibidores , Eritropoyetina/metabolismo , Depuradores de Radicales Libres/farmacología , Peróxido de Hidrógeno/farmacología , Hipoxia/metabolismo , Técnicas In Vitro , Masculino , Pirogalol/farmacología , ARN Mensajero/metabolismo , Ratas , Ratas Sprague-Dawley , Valores de Referencia , Tiourea/análogos & derivados , Tiourea/farmacología , Vitamina A/farmacología

RESUMEN

It was previously postulated on the basis of clinical data that the cardiovascular sequelae of extracorporeal whole-body hyperthermia (e-WBH), i.e., hypotension (which requires catecholamine support) results in unique nephrotoxicity in combination with select chemotherapeutic agents. In an attempt to explain this phenomenon, we mimicked e-WBH physiological conditions in a rat model. Animals were treated with and without ifosfamide (IFO) and/or carboplatin (CBDCA) at 37 degrees C or 41.5-41.8 degrees C, with blood pressure monitoring and catecholamine support comparable to the clinical setting. Ex vivo post-treatment data (24 h) from artificially perfused kidneys (i.e., histology, urine volume, perfusion rate, glomerular filtration rate, and the reabsorption of sodium, glucose, and water) demonstrated unique toxicity including proximal tubular necrosis for the combination of WBH and IFO, for WBH and CBDCA and for WBH and IFO plus CBDCA, but not for IFO and CBDCA without WBH. These data, considered together with results derived from a subsequent clinical trial and the laboratory work of others were consistent with the hypothesis.

Asunto(s)

Antineoplásicos Alquilantes/toxicidad , Antineoplásicos/toxicidad , Protocolos de Quimioterapia Combinada Antineoplásica/toxicidad , Carboplatino/toxicidad , Hipertermia Inducida/efectos adversos , Hipotensión/etiología , Ifosfamida/toxicidad , Enfermedades Renales/etiología , Animales , Antineoplásicos/administración & dosificación , Antineoplásicos/farmacología , Antineoplásicos Alquilantes/administración & dosificación , Antineoplásicos Alquilantes/farmacología , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Carboplatino/administración & dosificación , Carboplatino/farmacología , Terapia Combinada , Hipertermia Inducida/métodos , Hipotensión/inducido químicamente , Ifosfamida/administración & dosificación , Ifosfamida/farmacología , Enfermedades Renales/inducido químicamente , Enfermedades Renales/patología , Masculino , Ratas , Ratas Sprague-Dawley

RESUMEN

Proinflammatory cytokines play an important role in the pathogenesis of anemia in inflammatory diseases. Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) have been reported to inhibit the synthesis of erythropoietin (EPO) in vitro. To evaluate the in vivo significance of this observation, we have investigated effects of the administration of bacterial lipopolysaccharide (LPS) and IL-1 beta on renal EPO production in rats. Measurements by competitive reverse-transcription polymerase chain reaction showed that EPO mRNA levels were significantly reduced in the kidneys of normoxic rats 6 h after the injection of LPS (0.1 or 1 mg/kg). In addition, LPS and IL-1 beta (1 microgram/kg) inhibited the increase in EPO mRNA and plasma EPO levels when administered to rats before hypoxia exposure (8% O2 in the inspiratory gas). Evidence for an inflammatory reaction in the kidneys of LPS-treated rats was provided by measurements of greatly elevated renal TNF-alpha mRNA levels. Furthermore, kidneys isolated from LPS-created rats produced less immunoreactive EPO when perfused hypoxically in vitro for 2 h. Thus mediators of the immune response inhibit renal EPO gene expression in vivo, which is relevant with respect to the impaired synthesis of EPO in inflammatory diseases in humans.

Asunto(s)

Eritropoyetina/biosíntesis , Interleucina-1/farmacología , Riñón/fisiología , Lipopolisacáridos/farmacología , Transcripción Genética/efectos de los fármacos , Animales , Cartilla de ADN , Eritropoyetina/sangre , Escherichia coli , Tasa de Filtración Glomerular/efectos de los fármacos , Hipoxia , Riñón/efectos de los fármacos , Riñón/metabolismo , Cinética , Masculino , Reacción en Cadena de la Polimerasa , ARN Mensajero/biosíntesis , Ratas , Ratas Sprague-Dawley , Circulación Renal/efectos de los fármacos , Factor de Necrosis Tumoral alfa/biosíntesis , Resistencia Vascular/efectos de los fármacos

RESUMEN

An important role in O2 sensing has been assigned to microsomal and membrane-bound b-type cytochromes which generate regulatory reactive O2 species (ROS). Recently, ROS have been shown to suppress the in vitro synthesis of erythropoietin (Epo). We investigated the potential of the antioxidant vitamins A, E and C to enhance renal and hepatic Epo production. Renal effects were studied in isolated serum-free perfused rat kidneys. In control experiments without antioxidant vitamins, Epo secretion amounted to 441 +/- 23 mU/g kidney (mean +/- SEM, N = 5) during the three hour period of hypoxic perfusion (arterial pO2 35 mm Hg). Epo secretion significantly increased to 674 +/- 92 mU/g kidney (N = 7) when vitamins A (0.5 microgram/ml), E (0.5 microgram/ml) and C (10 micrograms/ml) in combination were added to the perfusion medium. The effects of the single vitamins were studied in Epo-producing hepatoma cell cultures (lines HepG2 and Hep3B). Vitamin A induced a dose-dependent increase (half-maximal stimulation at 0.2 microgram/ml) in the production of immunoreactive Epo during 24 hours of incubation (such as 680 +/- 51 U Epo/g cell protein in HepG2 cultures with 3 micrograms/ml retinol acetate compared to 261 +/- 15 U/g in untreated controls; N = 4). In contrast, vitamin E (tested from 0.05 to 500 micrograms/ml) and vitamin C (tested from 2 to 200 micrograms/ml) did not increase Epo production in hepatoma cell cultures. Thus, while vitamins E and C may have the potential to protect cells from oxidative damage, vitamin A exerts a specific stimulation of Epo production. Preliminary evidence suggests that this effect of vitamin A involves increased mRNA levels of hypoxia-inducible factor 1 alpha (HIF-1 alpha).

Asunto(s)

Antioxidantes/farmacología , Eritropoyetina/biosíntesis , Riñón/efectos de los fármacos , Riñón/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Factores de Transcripción , Vitaminas/farmacología , Animales , Ácido Ascórbico/farmacología , Línea Celular , Proteínas de Unión al ADN/genética , Expresión Génica/efectos de los fármacos , Humanos , Hipoxia/genética , Hipoxia/metabolismo , Factor 1 Inducible por Hipoxia , Subunidad alfa del Factor 1 Inducible por Hipoxia , Técnicas In Vitro , Masculino , Proteínas Nucleares/genética , Perfusión , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas , Ratas Sprague-Dawley , Vitamina A/farmacología , Vitamina E/farmacología

RESUMEN

The renal glycoprotein hormone erythropoietin (Epo) is the key element in the feedback control of the production of red blood cells (RBC) in bone marrow. Excess of antidiuretic hormone (ADH) increases the RBC mass by increasing the synthesis of Epo. The mechanism of the Epo stimulating effect of ADH is not fully understood. Rats were treated with ADH with or without prior injection of a V1a-receptor antagonist. Additional experiments were carried out by stimulating the V2-receptor by desmopressin (DDAVP). Epo level in plasma was doubled following injections of ADH. Blockade of the V1a-receptor completely abolished the Epo stimulating effect of ADH. Neither ADH alone nor the combined giving of V1a-antagonist and ADH had an influence on the glomerular filtration rate or the renal plasma flow. Therefore, the increased Epo synthesis after application of ADH cannot be explained by a constriction of renal blood vessels with consecutive ischemic hypoxia. There is rather a direct stimulation of Epo synthesis by ADH via its receptors. Since a selective stimulation of the V2-receptor by DDAVP did not increase to Epo level in plasma, the observed increase of Epo is mediated by the V1a-receptor.

Asunto(s)

Eritropoyetina/biosíntesis , Circulación Renal , Vasoconstricción/fisiología , Vasopresinas/farmacología , Animales , Antagonistas de los Receptores de Hormonas Antidiuréticas , Presión Sanguínea/efectos de los fármacos , Combinación de Medicamentos , Eritropoyetina/sangre , Tasa de Filtración Glomerular/efectos de los fármacos , Hematócrito , Masculino , Ratas , Ratas Sprague-Dawley , Receptores de Vasopresinas/fisiología , Circulación Renal/efectos de los fármacos

RESUMEN

In patients with the anemia of chronic diseases, the plasma level of EPO is often low in relation to the blood hemoglobin concentration. Because infectious and inflammatory processes cause activation of cytokine-producing macrophages and lymphocytes, we investigated whether isolated inflammatory cytokines influence the synthesis of EPO in vitro. IL-1 and TNF-alpha were shown to inhibit EPO mRNA levels and EPO formation in the human hepatoma cell cultures HepG2 and Hep3B, and to lower EPO formation in isolated perfused rat kidneys. IFN-alpha and IFN-beta also induced some inhibition of EPO production in HepG2 cultures. IL-3, TGF-beta 2, and IFN-gamma did not inhibit. IL-6 stimulated the production of EPO in Hep3B cells but was ineffective in HepG2 cells and lowered EPO production in isolated perfused rat kidneys. IL-1, TNF-alpha, and possibly other cytokines could contribute to defective EPO production in renal and nonrenal immune responses.

Asunto(s)

Anemia/fisiopatología , Citocinas/farmacología , Eritropoyetina/biosíntesis , Riñón/fisiología , Anemia/etiología , Animales , Carcinoma Hepatocelular , Línea Celular , Enfermedad Crónica , Medios de Cultivo Condicionados , Eritropoyetina/antagonistas & inhibidores , Eritropoyetina/farmacología , Hemoglobinas/metabolismo , Humanos , Inflamación , Interferón-alfa/farmacología , Interferón beta/farmacología , Riñón/efectos de los fármacos , Cinética , Neoplasias Hepáticas , Macrófagos Peritoneales/fisiología , Masculino , Ratones , Monocinas/farmacología , Consumo de Oxígeno , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes/farmacología , Células Tumorales Cultivadas

RESUMEN

Effects of thyroid hormones on the production of erythropoietin (Epo) were investigated in isolated perfused rat kidneys and in the human hepatoma cell line, HepG2. Epo protein was measured by radioimmunoassay. L-triiodothyronine and L-thyroxine stimulated hypoxia-induced Epo formation both in the kidney and in HepG2 cells in a dose-dependent fashion. Quantitation of Epo mRNA by competitive polymerase chain reaction (PCR) showed that hypoxic HepG2 cells had three-fold higher Epo messenger RNA levels when treated with thyroid hormones for 3 hours. Measurements of oxygen consumption revealed that this effect was not due to an increase in the degree of hypoxia. Thus, apart from the known direct effect on erythroid precursors, thyroid hormones appear to stimulate erythropoiesis by a noncalorigenic increase in Epo production.

Asunto(s)

Eritropoyetina/metabolismo , Hipoxia/fisiopatología , Tiroxina/farmacología , Triyodotironina/farmacología , Animales , Carcinoma Hepatocelular/química , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patología , Células Cultivadas , ADN/genética , Relación Dosis-Respuesta a Droga , Eritropoyetina/análisis , Eritropoyetina/genética , Humanos , Riñón/química , Riñón/citología , Riñón/metabolismo , Neoplasias Hepáticas/química , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patología , Masculino , Consumo de Oxígeno/fisiología , Reacción en Cadena de la Polimerasa , ARN Mensajero/análisis , ARN Mensajero/genética , Radioinmunoensayo , Ratas , Ratas Sprague-Dawley , Células Tumorales Cultivadas , alfa-Fetoproteínas/análisis , alfa-Fetoproteínas/genética , alfa-Fetoproteínas/metabolismo

RESUMEN

The glomerular permeability of the isolated perfused kidney is manifold higher than in vivo, although structural changes at the glomerular filtration barrier are not described. It has been proposed that in vivo high molecular weight plasma proteins are concentrated at the glomerular endothelium forming an additional filtration barrier ('concentration polarization'). To test this hypothesis, isolated rat kidneys were perfused with substrate-enriched Krebs-Henseleit solutions containing albumin (50 g/l) or albumin/globulin (40/10 g/l), or with plasma. The pO2 was 675 mm Hg. Furthermore, experiments were carried out with the addition of erythrocytes with and without a reduced O2 supply (pO2 35 mm Hg). Independent of the composition of the perfusate a continuously increasing glomerular permeability was observed immediately after perfusion was started. After about 10 min, a steady state value for the glomerular permeability was reached. The addition of globulin to the perfusate or perfusion with plasma did not prevent the initial increase of the permeability. However, after addition of 5% erythrocytes to the perfusate the increase of permeability was much less pronounced. Neither the reduction of the O2 supply nor the addition of erythrocytes to a higher concentration than 5% had any further effect on the glomerular permeability. These data show that concentration polarization of high molecular weight proteins does not take place at the endothelium of the glomerulus. Independent of their ability to carry O2 erythrocytes play an important role in the glomerular filtration process.

Asunto(s)

Glomérulos Renales/metabolismo , Proteínas/metabolismo , Albúminas/metabolismo , Animales , Eritrocitos/metabolismo , Globulinas/metabolismo , Humanos , Técnicas In Vitro , Masculino , Oxígeno/metabolismo , Perfusión , Permeabilidad , Ratas , Ratas Wistar

Asunto(s)

Eritropoyetina/biosíntesis , Hipoxia/fisiopatología , Riñón/fisiopatología , Oxígeno/sangre , Animales , Retroalimentación , Hematócrito , Técnicas In Vitro , Riñón/irrigación sanguínea , Masculino , Perfusión , Ratas , Ratas Sprague-Dawley

RESUMEN

The blood level of erythropoietin (Epo) is often anomalously low in anemic patients with inflammatory or malignant diseases. Therefore, we studied effects of pure recombinant immunomodulatory peptides on Epo formation in cultures of the human hepatoma cell line, HepG2. Interleukin (IL)-1 beta, IL-1 alpha, and tumor necrosis factor alpha lowered Epo production with half-maximal inhibition at 2, 5, and 20 U/ml, respectively. IL-6, transforming growth factor beta 2 and interferon gamma did not inhibit. Furthermore, IL-1 beta (10 U/ml) proved to block Epo formation in isolated serum-free perfused rat kidneys. Proposedly, monokines play a role in the pathogenesis of Epo deficiency in various diseases.

Asunto(s)

Carcinoma Hepatocelular/metabolismo , Eritropoyetina/biosíntesis , Riñón/metabolismo , Neoplasias Hepáticas/metabolismo , Monocinas/farmacología , Animales , Humanos , Técnicas In Vitro , Interferón gamma/farmacología , Interleucina-1/farmacología , Ratas , Proteínas Recombinantes , Factor de Crecimiento Transformador beta/farmacología , Células Tumorales Cultivadas

RESUMEN

The renal glycoprotein hormone erythropoietin (Epo) interacts with erythrocytic progenitors to stimulate their proliferation and differentiation in the bone marrow. The renal O2-sensing mechanism in the control of the synthesis of Epo is still poorly understood. Therefore, the capacity of isolated rat kidneys to produce Epo during hypoxic and anemic perfusion was studied. The kidneys were perfused at a constant perfusion pressure of 100 mm Hg with a substrate-enriched Krebs-Henseleit solution containing 60 g/liter BSA and freshly drawn human erythrocytes. Epo was measured by RIA. When the kidneys were perfused at an arterial pO2 of 720 or 150 mm Hg (hematocrit, 5%), Epo production was very low (0.1-0.2 U/g kidney within 3 h of perfusion). When the arterial pO2 was lowered to 35 or 20 mm Hg, Epo production increased to 0.4 and 0.9 U/g kidney, respectively. The release of Epo during hypoxic perfusion (pO2 35 and 20 mm Hg) was little affected by changes in the hematocrit, i.e. the O2-carrying capacity of the perfusion medium over a wide range (0-40%). These results indicate that the production of Epo in the isolated perfused kidney depends on the availability of O2 and can be modulated by changes in the arterial pO2.

Asunto(s)

Eritropoyetina/metabolismo , Hipoxia/metabolismo , Riñón/metabolismo , Anemia/metabolismo , Animales , Hematócrito , Técnicas In Vitro , Masculino , Perfusión/métodos , Radioinmunoensayo , Ratas , Ratas Endogámicas

RESUMEN

In order to further investigate the dependency of the production of erythropoietin (Epo) on the renal O2 supply, experiments were carried out in the isolated perfused rat kidney (IPRK). The kidneys were perfused with a substrate enriched Krebs-Henseleit solution containing 60 g/l bovine serum albumin at a constant perfusion pressure of 100 mmHg. When the kidneys were perfused at an arterial pO2 of 720 or 150 mmHg (hematocrit 5%), Epo production measured by RIA was very low (0.1-0.2 U/g kidney after 3 h of perfusion). At a pO2 of 20 mmHg, Epo production increased markedly up to 0.9 U/g kidney. However, the production of Epo was little affected by changes in the hematocrit of the perfusion medium from zero to 40%, even if severe anemia was mimicked. These results indicate that Epo production in the IPRK is mainly under the control of the arterial pO2.

Asunto(s)

Eritropoyetina/biosíntesis , Riñón/metabolismo , Anemia/metabolismo , Animales , Hematócrito , Masculino , Perfusión , Ratas , Ratas Endogámicas