AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 5 1454-R1462, Copyright © 1994 by American Physiological Society
Circadian rhythms and time course of adaptive sodium and potassium excretion in rats after uninephrectomy
R. I. Aizman, L. Rabinowitz and C. Mayer-Harnisch
Department of Human Physiology, University of California, Davis 95616.
The relationship between renal circadian cyclic excretion and renal
compensatory adaptation after uninephrectomy for K, Na, and water was
studied. Rats in a 12:12-h light-dark environment were given a liquid diet,
and urine was collected for 16 days with consecutive 90-min periods. Days
1-4 were control, 5-10 followed a sham operation, and 11-16 followed
uninephrectomy. The major findings were 1) the circadian cycles in
excretion were virtually unchanged after sham and uninephrectomy; 2) an
adaptive increase in excretion of Na, K, and water by the remaining kidney
occurred within 90 min after uninephrectomy; 3) after uninephrectomy the
distribution of the 24-h increment in excretion for the remaining kidney
closely followed the preexisting pattern of circadian excretion for Na but
was evenly distributed between light and dark phases for K; and 4) after
uninephrectomy the ratio of excretion to intake was unchanged. This is the
first study to document the time course of adaptation to uninephrectomy
using consecutive brief collections over several days in unanesthetized and
undisturbed rats. Adaptation after uninephrectomy occurred essentially
immediately; was maintained unchanged; and preserved Na, K, and water
homeostasis. Uninephrectomy did not alter the circadian control of
excretion.
