Corticosteroid induction of renal and intestinal K+-dependentp-nitrophenylphosphatase in young and adult rats |
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Institution: | (1) Institute of Physiology, Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague 4, Czech Republic |
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Abstract: | Summary The post-natal development of the K+-dependentp-nitrophenylphosphatase (K-NPPase) activity of the Na, K-ATPase complex and its regulation by corticosteroids was studied
in renal and intestinal epithelia of the rat using thep-nitrophenylphosphatecerium capture method. The distribution of the phosphatase was analysed in detail in the renal epithelia
of the medullary thick ascending limb of Henle's loop and distal convoluted tubule and in the surface epithelial cells of
the distal colon. The convoluted tubule and Henle's loop segments showed a stronger reaction for K-NPPase than the colon epithelium
both in adult and young animals (suckling and weanling pups). The intensity of staining rose progressively in all three epithelia
during early postnatal development and reached the highest levels during the weaning period and in adulthood. The most distinct
change was observed between days 10 and 16. Adrenalectomy significantly reduced the density of the final reaction product
in weanling and adult rats. Replacement hormone therapy of adrenalectomized weanling rats with the glucocorticoid dexamethansone
restored the K-NPPase activity in the two renal epithelia, whereas the mineralocorticoid deoxycorticosterone acetate had no
effect on the activity in the medullary thick ascending limb, a very slight effect in distal convoluted tubules, and a strong
effect on the distal colon epithelial activity. The observed small effect of the mineralocorticoid in distal convoluted tubule
activity may reflect a cross-over into glucocorticoid receptors. We conclude that the postnatal development of Na,K-ATPase
is regulated by glucocorticoids in nephron epithelia and predominatly by mineralocorticoids in the surface enterocytes of
the distal colon. |
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