RESUMO

High sugar-sweetened beverage intake has been related to human kidney disease and metabolic alterations. We determine the impact of high sucrose intake from pregnancy until early postnatal days and post-weaning on kidneys from adult male offspring rats. Wistar female rats were mated and assigned into two groups: one control drinking tap water (CM) and another drinking 5 % sucrose diluted in water (SM). Two offspring per mother were randomly allocated into two experimental groups at weaning. One had free access to simple water (CO) and the other to 5 % sucrose (SO) for 14 weeks. After treatment, levels of relative aquaporin-2 (AQP2), glomerulosclerosis index (GI), collecting tube area, perirenal fat, blood creatinine, and blood ureic nitrogen concentration (BUN) were determined. Two-way ANOVA followed by Bonferroni post-hoc test was used, considering P ≤ 0.05 as a significant statistical difference. Sucrose consumption during gestation/lactation and interaction increased AQP2 expression in the renal cortex and BUN concentration. In contrast, gestation/lactation consumption increased collecting tube area, post-weaning consumption favored perirenal fat, and finally, gestation/lactation, post-weaning, and the interaction caused glomerulosclerosis. Our results suggest that the consumption of sucrose water during gestation/lactation or post-weaning or combination triggers pathological changes in the kidneys of adult rats.

Assuntos

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Methotrexate (MTX) is a derivate of folic acid, commonly used as an anchor drug for the treatment and management of malignant diseases and autoimmune disorders. However, nephrotoxicity is an important drawback of MTX therapy. Unfortunately, there are not enough studies reporting the nature of the renal failure induced by MTX. Thus, the aim of this study was to evaluate the time course of renal handling of water and electrolytes in male Wistar rats, after the exposure to a unique dose of MTX (80 mg/kg b.w.). Experiments were carried out at day 2, day 4, day 8 and day 14 after MTX administration. Several parameters of kidney function related to water and electrolytes handling were evaluated. Renal expression and urinary excretion of aquaporin-2 (AQP2) and Na-K-2Cl-cotransporter (NKCC2) were determined by Western blotting. MTX produced alterations on water handling on the second day after treatment, showing a significant increase in solute free water reabsorption which might be mediated by the increased expression of AQP2 in apical membranes. On the other hand, MTX produced alterations on electrolytes handling on the fourth day after treatment, showing a significant decrease of sodium chloride excretion, mediated at least in part, by the increase renal expression of NKCC2. These results provide valuable information to clinical practice in order to be able to find therapeutic targets that diminish adverse effects and health deterioration. Moreover, MTX treatment altered AQP2 and NKCC2 urinary excretion allowing postulating these transporters as potential biomarkers of MTX induced nephrotoxicity.

Assuntos

RESUMO

SUMMARY: Aquaporins (AQPs) are members of the aquaporin water channel family that play an important role in reabsorption of water from the renal tubular fluid to concentrate urine. Using immunohistochemical staining on paraffin sections, We studied expression of AQP2, AQP3 and AQP4 in renal medulla of Bactrian camel (Camelus bactrianus). The renal medulla of cattle (Bos taurus) acted as the control. Compared with the control, strong expression of AQP2 was observed at the apical plasma membrane and intracellular vesicles, in both the outer medullary collecting duct (OMCD) and the inner medullary collecting duct (IMCD) of camel. Strong expression of AQP3 was observed at the basolateral plasma membrane of the IMCD of camel. Strong AQP4 expression, however, was observed at the basolateral plasma membrane in the OMCD of camel. Moreover, moderate AQP4 expression was detected in endothelium of capillary in medullary region of camels, whereas very weak/absent expression was detected in endothelium of capillary of cattle. We concluded that expression of AQP2, AQP3 and AQP4 in the camel kidney showed some differences from cattle in renal trans-epithelial water transport. It may enhance our better understanding of special water metabolism mechanisms that enable camels to survive in extreme environments.

RESUMEN: Las acuaporinas (AQP) son miembros de las proteínas de transporte que desempeñan un papel importante en la reabsorción de agua del líquido tubular renal para concentrar la orina. Estudiamos la expresión de AQP2, AQP3 y AQP4 en la médula renal del camello bactriano (Camelus bactrianus) usando tinción inmunohistoquímica en secciones de parafina. La médula renal del bovino (Bos taurus) se usó como control. En comparación con el control, se observó una fuerte expresión de AQP2 en la membrana plasmática apical y vesículas intracelulares tanto en el conducto colector medular externo (CCME) como en el conducto colector medular interno (CCMI) del camello. Se observó una fuerte expresión de AQP3 en la membrana plasmática basolateral del CCMI del camello. También se observó una expresión fuerte de AQP4 en la membrana plasmática basolateral en el CCME de camello. Además, se detectó una expresión moderada de AQP4 en el endotelio de los capilares en la región medular de los camellos, mientras que en el endotelio de los capilares del bovino se detectó una expresión muy débil. Concluimos que la expresión de AQP2, AQP3 y AQP4 en el riñón de camello mostró algunas diferencias con el bovino en el transporte trans-epitelial de agua renal. El estudio podría mejorar nuestra comprensión de los mecanismos especiales del metabolismo del agua que permiten a los camellos sobrevivir en ambientes extremos.

Assuntos

RESUMO

ABSTRACT Aquaporin 2 (AQP2) is a small protein located in the collecting tubules of kidneys; it plays an important role in the concentration and production of urine. The aim of this study was to determine the expression level of the AQP2 gene in the kidney of broiler chickens after the administration of renal­dose dopamine. Broiler chickens (25 days-old) were randomly divided into two groups (n=20 per group): intravenous administration of saline solution (control group) or renal-dose dopamine (dopamine group). The expression and localization of the AQP2 gene were evaluated by real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC), respectively. The protein level of AQP2 was analyzed by western blot analysis. The dopamine group presented no significant difference (p>0.05) in the biochemical criterion or mRNA expression of AQP2 compared with the control group. However, AQP2 protein level was significantly reduced (p 0.05) in the membrane of renal tubular epithelial cells. In contrast, protein level was significantly increased (p 0.05) in the cytoplasm of the dopamine group compared with the control group. Moreover, AQP2 protein was apparently more distributed and localized in the cytoplasmic vacuoles than in the membranes of the kidney in the renal­dose dopamine administered chickens group. In conclusion, present findings suggest that renal­dose dopamine mediates the level of AQP2 protein via shuttle from the cell membrane to the cytoplasm rather than changing the expression of AQP2 gene to adjust the secretion and absorption of water in kidney.(AU)

Assuntos

RESUMO

ABSTRACT Aquaporin 2 (AQP2) is a small protein located in the collecting tubules of kidneys; it plays an important role in the concentration and production of urine. The aim of this study was to determine the expression level of the AQP2 gene in the kidney of broiler chickens after the administration of renal­dose dopamine. Broiler chickens (25 days-old) were randomly divided into two groups (n=20 per group): intravenous administration of saline solution (control group) or renal-dose dopamine (dopamine group). The expression and localization of the AQP2 gene were evaluated by real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC), respectively. The protein level of AQP2 was analyzed by western blot analysis. The dopamine group presented no significant difference (p>0.05) in the biochemical criterion or mRNA expression of AQP2 compared with the control group. However, AQP2 protein level was significantly reduced (p 0.05) in the membrane of renal tubular epithelial cells. In contrast, protein level was significantly increased (p 0.05) in the cytoplasm of the dopamine group compared with the control group. Moreover, AQP2 protein was apparently more distributed and localized in the cytoplasmic vacuoles than in the membranes of the kidney in the renal­dose dopamine administered chickens group. In conclusion, present findings suggest that renal­dose dopamine mediates the level of AQP2 protein via shuttle from the cell membrane to the cytoplasm rather than changing the expression of AQP2 gene to adjust the secretion and absorption of water in kidney.

Assuntos

RESUMO

BACKGROUND/AIMS: We have previously shown that aquaporin-2 (AQP2) is down-regulated in the renal medulla of rats made hypertensive by chronic inhibition of nitric oxide synthase. It has been shown that AQP2 expression is regulated by the calcineurin/nuclear factor of activated T cells (NFATc). Nitric oxide (NO) regulates the activity of NFATc via c-Jun-N-terminal kinase 2 (JNK2). Therefore, we hypothesized that increases in NO enhance NFATc-mediated up-regulation of AQP2 promoter activity. METHODS: AQP2 mRNA and protein expression were detected in mouse renal papilla. AQP2 promoter luciferase reporter- and NFAT luciferase reporter-transfected MDCK cells were used to determine AQP2 promoter activity and NFATc activity, respectively. Cells were incubated with classic activators and inhibitors of NFATc and the NO pathway. RESULTS: Our results demonstrate that both Ca(2+) and NO have a synergistic effect resulting in an increase in AQP2 mRNA and protein in mouse papilla and activation of the AQP2 promoter in kidney-derived cells. In addition, NO enhances Ca(2+)-induced NFATc activation. The underlying mechanism involves increased NFATc nuclear import and decreased export via protein kinase G-mediated inhibition of JNK1/2. CONCLUSIONS: This is the first study defining novel regulatory roles for NO and NFATc in the control of AQP2, which is an important renal protein.