Ri. Aizman et al., CIRCADIAN-RHYTHMS AND TIME-COURSE OF ADAPTIVE SODIUM AND POTASSIUM EXCRETION IN RATS AFTER UNINEPHRECTOMY, The American journal of physiology, 266(5), 1994, pp. 180001454-180001462
The relationship between renal circadian cyclic excretion and renal co
mpensatory adaptation after uninephrectomy for K, Na, and water was st
udied. Rats in a 12:12-h light-dark environment were given a liquid di
et, and urine was collected for 16 days with consecutive 90-min period
s. Days 1-4 were control, 5-10 followed a sham operation, and 11-16 fo
llowed 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 remain
ing kidney occurred within 90 min after uninephrectomy; 3) after unine
phrectomy 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 ph
ases for K; and 4) after uninephrectomy the ratio of excretion to inta
ke was unchanged. This is the first study to document the time course
of adaptation to uninephrectomy using consecutive brief collections ov
er several days in unanesthetized and undisturbed rats. Adaptation aft
er uninephrectomy occurred essentially immediately; was maintained unc
hanged; and preserved Na, K, and water homeostasis. Uninephrectomy did
not alter the circadian control of excretion.