AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 3 441-R449, Copyright © 1986 by American Physiological Society
Circadian urinary excretion rhythms in adrenalectomized rats
J. A. Poulis, F. Roelfsema and D. van der Heide
The impact of the adrenal system on urinary rhythms was investigated in
adrenalectomized (ADX) rats under various experimental conditions. During a
12:12 light-dark cycle the acrophases were shifted in ADX rats with respect
to control rats. Under constant light conditions ADX rats displayed
free-running rhythms, similar to those of control rats. The periods were
stable in blind rats but not in rats maintained on a constant light cycle.
The abrupt change in period, which occurred after approximately 8 days,
suggests a stage of internal desynchronization. A 6-h delay in the
administration of corticosterone to ADX rats caused a delay shift of the
acrophases. A single intraperitoneal injection of corticosterone in blind
free-running ADX rats caused delay or advance shifts so that we could
construct phase-response curves for the various excretory rhythms. These
observations indicate that the adrenals are not essential for the
establishment of the urinary rhythms; however, corticosterone influences
the phase setting of these rhythms. The site of action is probably the X
pacemaker (controlling the body temperature rhythm), although we cannot
totally exclude an additional effect on secondary (renal) oscillators.
