AJP - Regulatory, Integrative and Comparative Physiology, Vol 240, Issue 3 175-R181, Copyright © 1981 by American Physiological Society
Role of aldosterone in sodium retention of pregnancy in the rat
S. Churchill, H. H. Bengele, J. C. Melby and E. A. Alexander
The purpose of this study was to test whether the absence or inhibition of
aldosterone would alter the Na retention of pregnancy in the rat. We
performed metabolic balance studies during the last 2 wk of the 3-wk rat
pregnancy in the following four groups of saline-drinking rats:
nonpregnant, sham adrenalectomized; pregnant, sham adrenalectomized;
nonpregnant, adrenalectomized; and pregnant, adrenalectomized. Significant
net Na retention was not found during the 2nd wk in any of the groups.
During the final week, however, both pregnant groups retained between 8 and
11 meq Na more than their respective control groups. In addition, we
measured plasma aldosterone concentration in these rats at term. The
mineralocorticoid was not detectable in the nonpregnant adrenalectomized
rats but was present in the pregnant adrenalectomized rats at a
concentration of about 50% of that found in the pregnant
sham-adrenalectomized rats. Serial measurements revealed that aldosterone
was measurable by day 18 and nondetectable by 2 days postpartum in these
pregnant adrenalectomized rats. Comparable balance studies were also
performed in three groups of water-drinking rats: nonpregnant, pregnant,
and pregnant rats that received large daily doses of spironolactone. During
the 3rd wk both pregnant groups were in significant positive Na balance.
Net Na retention for untreated pregnant rats was 8.4 meq and for the
spironolactone treated, 6.9 meq, values that were not significantly
different. We conclude that is is unlikely that aldosterone plays a
critical role in the Na retention found during rat pregnancy.
