AJP - Renal Physiology, Vol 241, Issue 3 273-F278, Copyright © 1981 by American Physiological Society
Short-term effect of aldosterone on Na-K-ATPase in single nephron segments
A. Doucet and A. I. Katz
One of the theories proposed to explain the action of mineralocorticoids on
target tissues attributes their effect on cation transport to stimulation
of the "sodium pump." To test this hypothesis we evaluated the short-term
effect of aldosterone on Na-K-ATPase in discrete nephron segments
microdissected from kidneys of adrenalectomized animals. Na-K-ATPase
activity measured in proximal and distal nephron segments from
adrenalectomized as well as intact mice remained unchanged 1 or 3 h after a
single injection of D-aldosterone (10 micrograms/100 g body wt i.p.).
Similarly, no effect of aldosterone could be demonstrated in experiments in
vitro, in which tubules from adrenalectomized mice and rabbits were
incubated (90 min, 37 degrees C) in the presence of physiologic or
pharmacologic concentrations of the hormone (3.10(-10) to 3.10(-6) M).
These studies did not show an effect of aldosterone on isolated tubule
Na-K-ATPase within the time interval in which this hormone alters tubular
cation transport and therefore do not support the "pump theory" of
mineralocorticoid action.
