AJP - Renal Physiology, Vol 244, Issue 4 383-F391, Copyright © 1983 by American Physiological Society
Effect of potassium on renal NH3 production
S. Sastrasinh and R. L. Tannen
The influence on renal ammoniagenesis of a high potassium diet and also of
acute manipulation of ambient potassium concentration was investigated
using both the isolated perfused rat kidney and incubated renal cortical
tubules. Ingestion of a high potassium diet for 1 wk resulted in potassium
adaptation but had no effect on ammonia production by the isolated kidney
perfused with physiologic concentrations of glutamine. By contrast,
perfusion with a high ambient potassium concentration (8.0-9.3 mM)
significantly increased renal tissue potassium levels and concomitantly
reduced the rate of ammonia formation by 30% in comparison with perfusions
at a normal potassium concentration. NH3 production by tubules incubated
with 1 mM glutamine was also decreased at a K+ concentration of 9.0 mM.
Ammonia production was unchanged when kidneys were perfused with a
potassium concentration of 2.0 mM despite a 16% decrease in renal tissue
potassium levels, but ammonia production by tubules incubated in 2 mM K+
was slightly less than in control incubations at 5.0 mM. Thus, unlike
earlier in vitro studies with outer medullary slices, these studies do not
support the hypothesis that an adaptive change in ammoniagenesis results
from a high dietary potassium intake. However, a high ambient and renal
intracellular potassium concentration can depress ammonia production.
Although potassium depletion causes an adaptive increase in ammonia
production, a decrease in ambient potassium concentration does not increase
ammoniagenesis. Accordingly, both a potassium surfeit and deficit can
modify renal ammonia production, but the mechanisms involved appear to
differ.
