RESUMO
The effect of chronic high plasma corticosteroids' concentration upon renal function was studied in rats bearing a transplantable pituitary mammotropic tumor which produces large quantities of ACTH and prolactin (MtTF4S). Kidney splanchnomegaly and degenerative changes of renal cortex, particularly in proximal tubules, as well as cytolysis and appearance of vacuoles were noticed in tumor bearing rats. (Na+ + K+)-ATPase activity in renal plasma membranes decreased 67% in rats with a tumor secreting ACTH and prolactin, and 64% in rats with a tumor secreting growth hormone and prolactin when compared with controls. After adrenalectomy of MtTF4S rats, kidney weight as well as plasma concentrations of urea, sodium, chloride and phosphate ions were normalized indicating the involvement of adrenal glands in the development of disturbances in renal function.
Assuntos
Hormônio Adrenocorticotrópico/metabolismo , Córtex Renal/patologia , Síndromes Endócrinas Paraneoplásicas , Neoplasias Hipofisárias/metabolismo , Prolactina/metabolismo , Glândulas Suprarrenais/metabolismo , Glândulas Suprarrenais/fisiopatologia , Adrenalectomia , Animais , Peso Corporal , ATPase de Ca(2+) e Mg(2+)/metabolismo , Feminino , Hormônio do Crescimento/metabolismo , Córtex Renal/enzimologia , Tamanho do Órgão , Neoplasias Hipofisárias/patologia , Ratos , ATPase Trocadora de Sódio-Potássio/metabolismoRESUMO
The treatment of rat kidney plasma membranes with sodium dodecyl sulphate (SDS) did not essentially affect the ability of the membranes for 3H-aldosterone binding as compared with the intact plasma membranes (Ozegovic et al., 1977). A gel filtration of 3H-aldosterone-kidney plasma membranes complex on Sepharose 6B yielded 2 protein and 2 3H-aldosterone peaks. The proteins which were eluted in the first peak were associated with the first 3H-aldosterone peak while the second 3H-aldosterone peak was eluted with Ve corresponding to Ve of free 3H-aldosterone. Spironolactone, a competitive antagonist of aldosterone, prevented the binding of 3H-aldosterone to the membrane proteins. The results demonstrated a high affinity of the kidney plasma membranes solubilized with SDS and a specificity of aldosterone binding to the plasma membrane proteins of higher molecular mass.
Assuntos
Ligação Competitiva/efeitos dos fármacos , Rim/citologia , Proteínas de Membrana/metabolismo , Adrenalectomia , Aldosterona/metabolismo , Animais , Cromatografia em Gel , Cinética , Masculino , Ratos , Ratos Endogâmicos , Dodecilsulfato de Sódio , Solubilidade , Espironolactona/farmacologia , TrítioRESUMO
The enzymatic differentiation of various tissues is under hormonal control in the perinatal period. Since the regulation of Na+/K+-ATPase has not been explored prenatally, the aim of this study was to determine the corticosteroid sensitivity of sodium pump maturation in the fetal period. Na+/K+-ATPase activity was both measured in kidney homogenates of fetal rats and localized by in-situ histochemistry. Sodium pump activity was first quantifiable on day 18 of fetal development as 1.4 +/- 0.17 mumol Pi/h per mg protein, and was increased 3.4-times by day 22 of gestation. While the Na+/K+-ATPase activity was the most intense in cortical tubules at an earlier fetal age (18th and 19th day), the reaction product in the medullary tubules increased with fetal age, becoming highly intense on the 21st and 22nd day of gestation. From the 18th to 21st day of fetal development homogenate Na+/K+-ATPase activity increased as a function of chronologic age. While mineralocorticoids were without any effect on Na+/K+-ATPase activity, on the last day of the fetal development, the glucocorticoid dexamethasone proved to be successful in stimulating enzyme activity in corticosteroid-suppressed animals. According to our results, glucocorticoid hormones seem to be operating as an endogenous driving force for sodium pump maturation at the end of fetal development.
Assuntos
Corticosteroides/farmacologia , Rim/embriologia , ATPase Trocadora de Sódio-Potássio/metabolismo , 4-Nitrofenilfosfatase/metabolismo , Adrenalectomia , Animais , ATPase de Ca(2+) e Mg(2+)/metabolismo , Desoxicorticosterona/farmacologia , Desenvolvimento Embrionário e Fetal , Feminino , Rim/efeitos dos fármacos , Rim/enzimologia , Metirapona/farmacologia , Gravidez , Ratos , Ratos Endogâmicos F344RESUMO
The postnatal development of the sodium transport mechanism in the rat kidney, as judged by the activity of renal plasma membrane Na-K-ATPase, was studied. Highly purified kidney plasma membranes as verified by electron microscopic and enzyme examinations, were used. Na-K-ATPase activity (mumol Pi/mg protein/h) increases exponentially from 16.9 +/- 1.94 found at birth to the mature level of 43.1 +/- 2.16 reached at the age of 41 days. This finding paralleled our results of SDS-polyacrylamide gel disc electrophoresis, showing a completely differentiated plasma membrane protein structure at birth, the maturation of which proceeds only as quantitative enrichment of some protein fractions in the further postnatal period.
