AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 2 434-R442, Copyright © 1996 by American Physiological Society
Early effects of uninephrectomy on K homeostasis in unanesthetized rats
R. I. Aizman, L. Rabinowitz and C. Mayer-Harnisch
Department of Human Physiology, University of California, Davis 95616, USA.
Mechanisms underlying the change in K excretion (UKV) during the first 6
days after uninephrectomy (UNX) were examined in unanesthetized rats.
Arterial plasma K concentrations (PK) were 0.55 meq/l above control values
at 12 and 24 h after UNX but were not significantly different 36-72 h after
UNX. To determine if there was an increased sensitivity of the distal K
secretory mechanism to increases in PK, an intragastric KCl infusion was
given. The delta UKV/delta PK per kidney values were in the following
order: 6-day UNX > 2-day UNX > control. In the normal rats, an acute
increase of 0.5 meq/l in PK increased UKV by an amount approximating 25% of
the increase in UKV observed 12-24 h after UNX. Amiloride, administered 48
h after UNX, increased Na excretion per kidney and decreased UKV per kidney
approximately twice as much in UNX as in control groups. Thus an adaptive
increase of amiloride-inhibitable K secretion occurred within 2 days of UNX
and continued to increase thereafter. This K adaptation may have been
induced by transient increases in PK.
