AJP - Renal Physiology, Vol 266, Issue 3 419-F424, Copyright © 1994 by American Physiological Society
Collecting duct changes in potassium depletion: effects of ACE inhibition
S. K. Mujais
Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611.
Potassium depletion is associated with a hyperreninemia that may be
responsible for some of the renal hemodynamic and functional changes
observed in K-deficient states. The present study was designed to evaluate
whether interruption of the renin-angiotensin system with enalapril alters
the collecting duct changes observed in K depletion. Adrenalectomized male
Sprague-Dawley rats were allocated to either a normal (NK) or low-K diet
(LK), and they either received enalapril or vehicle for 3 wk. Na:K pump
activity (pmol.mm-1.h-1) in microdissected cortical collecting (CCT) and
medullary collecting tubules (MCT) was determined at 21 days after group
allocations. K depletion had a minimal effect on CCT outer diameter. In
contrast, a marked hypertrophy was observed in the MCT diameter (91%
increase, P < 0.001) that was significantly attenuated by enalapril
treatment (56% increase, P < 0.001 vs. LK). An increase in Na:K pump
activity was observed with LK, in the CCT from 497 +/- 47 to 1,089 +/- 83
(P < 0.001) and in the MCT from 489 +/- 36 to 1,396 +/- 45 pmol.mm-1.h-1
(P < 0.01). In K-replete rats, enalapril had no effect on Na:K pump
activity in either CCT or MCT. Enalapril administration during LK had no
effect on the increase in Na:K pump activity in the CCT (1,023 +/- 75
pmol.mm-1.h-1, P < 0.001), not different from LK alone. In the MCT,
however, enalapril reduced the increment in Na:K pump activity induced by
LK (1,116 +/- 39 pmol.mm-1.h-1, less than the change with LK
alone).(ABSTRACT TRUNCATED AT 250 WORDS)
