AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 6 1025-R1031, Copyright © 1987 by American Physiological Society
Rats with regenerating adrenals are more hypertensive in the morning than afternoon
R. Foulkes, S. M. Gardiner and T. Bennett
In rats following unilateral nephroadrenalectomy and contralateral adrenal
enucleation, adrenocortical tissue regenerates and secretes some steroids
in abnormal amounts but with a diurnal rhythmicity. This study investigated
whether the level of blood pressure (BP) in these rats also varies with the
time of day. Systolic BP was measured by the tail-cuff method twice daily
[between 0700 and 1000 h (A.M.) and again between 1400 and 1700 h (P.M.)]
in conscious Wistar rats before and after unilateral nephroadrenalectomy
and either contralateral adrenal-enucleation (AE) or sham-operation (SO);
all rats were given 1% NaCl to drink postoperatively. During the 4th wk
after surgery, systolic BP in AE rats was higher than in SO rats at both
times of day, but the difference was greater A.M. (SO = 142 +/- 2 mmHg, AE
= 176 +/- 4 mmHg) than P.M. (SO = 138 +/- 2 mmHg, AE = 150 +/- 2 mmHg). The
hypertension and the A.M.-P.M. changes in BP in AE rats were also seen with
intra-arterial recording. These phenomena were not directly associated with
changes in plasma volume, plasma Na+ concentration, or in the plasma levels
of corticosterone or 18-hydroxydeoxycorticosterone.
