AJP - Renal Physiology, Vol 251, Issue 2 199-F207, Copyright © 1986 by American Physiological Society
Regulation of renal Na+-K+-ATPase in the rat: role of increased potassium transport
S. K. Mujais, M. A. Chekal, J. P. Hayslett and A. I. Katz
The purpose of this study was to characterize the alterations in collecting
tubule Na+-K+-ATPase activity produced by sustained increments in dietary
potassium in the rat and to evaluate the role of aldosterone in their
generation. In adrenal-intact animals, feeding a high-potassium diet
(10-fold that of control) or administration of a high physiological dose of
aldosterone (5 micrograms X 100 g-1 X day-1), which simulates the delivery
rate of this hormone during potassium loading (both for 7 days), caused
marked increments in Na+-K+-ATPase activity in the cortical collecting
tubule (CCT) but had no effect on the enzyme in the inner stripe of the
medullary collecting tubule (MCT). A significant increase in enzyme
activity was also observed after smaller dietary potassium increments (2.5
and 5 times the control) and after 4 (but not 2) days of dietary potassium
load. In adrenalectomized rats provided with physiological replacement
doses of corticosterone and aldosterone (0.8 micrograms X 100 g-1 X day-1),
Na+-K+-ATPase activity in both CCT and MCT was similar to that of
adrenal-intact controls but remained unchanged after 7 days on the
potassium-enriched (10-fold) diet. In contrast, adrenalectomized animals
receiving the high physiological dose of aldosterone displayed an increase
in Na+-K+-ATPase activity of CCT comparable with that of adrenal-intact
animals, whereas the enzyme activity in the MCT was unaffected. In
conclusion, 1) following chronic potassium loading Na+-K+-ATPase activity
increases significantly in the CCT with no change in its activity in the
inner stripe of the MCT.(ABSTRACT TRUNCATED AT 250 WORDS)
