AJP - Renal Physiology, Vol 248, Issue 2 219-F227, Copyright © 1985 by American Physiological Society
Effects of aldosterone on potassium recycling in the kidney of adrenalectomized rats
E. Higashihara and J. P. Kokko
Recent studies have suggested that potassium, like urea, undergoes
medullary recycling. The present cortical and papillary micropuncture
studies were designed to confirm the existence of medullary potassium
recycling and to determine whether acute infusions of aldosterone affected
this phenomenon. Thus, nephron segmental analysis of potassium and sodium
transport was conducted in adrenalectomized Munich-Wistar rats and
similarly prepared rats that received aldosterone acutely to achieve
physiological blood levels. The clearance results demonstrated that
aldosterone has an acute antinatriuretic and a kaliuretic effect, whereas
the micropuncture studies demonstrated that 1) aldosterone increases
potassium secretion between early and late distal tubule punctures; 2)
aldosterone causes an increase in delivery of potassium to the papillary
collecting duct; 3) aldosterone does not increase potassium secretion
across the papillary collecting duct; and 4) aldosterone significantly
increases medullary potassium recycling as evidenced by increased
quantities of potassium present at the bend of the loop of Henle in
response to aldosterone infusions. Thus, the studies confirm the existence
of potassium recycling and suggest that this phenomenon is a feedback
system that, in part, regulates urinary potassium excretion.
