AJP - Renal Physiology, Vol 232, Issue 2 128-F135, Copyright © 1977 by American Physiological Society
Renal electrolyte circadian rhythms: independence from feeding and activity patterns
M. C. Moore-Ede and J. A. Herd
The interrelationships between urinary electrolyte circadian rhythms and
rhythms of feeding, drinking and activity were studied in six conscious
chair-acclimatized squirrel monkeys (Saimiri sciureus) kept in
temperature-controlled isolation chambers on a light-dark (LD) 12:12 h
cycle. With lights on (600 lx) from 0800 to 2000 h and off (less than 1 lx)
from 2000 to 0800 h, renal potassium excretion in monkeys fed ad libitum
fell to a daily minimum of 64 +/- 6 mueq/h at 0500 h and rose to a maximum
of 274 +/- 13 mueq/h at 1700 h. Sodium excretion fell to a minimum of 13
+/- 2 mueq/h at 1000 h and rose to a maximum of 43 +/- 6 mueq/h at 2100 h,
while water excretion fell to a minimum of 869 +/- 63 mul/h at 0500 h and
rose to a maximum of 2,307 +/- 222 mul/h at 1700 h. Feeding, drinking, and
activity occurred only during the lights-on period. Independence of the
urinary rhythms from diurnal variations in feeding, drinking, and activity
was established a) by depriving monkeys of food, b) by depriving monkeys of
water, and c) by training monkeys to perform a 2-hourly schedule of
feeding, drinking, and activity throughout day and night. None of these
three regimens resulted in major reductions of the amplitude, or changes in
the phase of the circadian rhythms of urinary electrolyte or water
excretion. These findings indicate that the circadian rhythms of urinary
potassium, sodium, and water excretion are controlled by mechanisms that
are not passively dependent on the behavioral patterns of feeding,
drinking, and activity.
