AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 1 199-R206, Copyright © 1996 by American Physiological Society
Involvement of type I corticosteroid receptor in the effects of ovariectomy on energy balance
A. Dagnault, Y. Deshaies and D. Richard
Department de Physiologie, Faculte Medecine, Universite Laval, Quebec, Canada.
The effects of the glucocorticoid receptor antagonist, RU-38486 (RU-486),
and the mineralocorticoid receptor (MR) antagonist, RU-28318, on energy
balance were investigated in a 2 [surgery: ovariectomy (OVX) and sham
operation] x 3 (corticosteroid antagonist: placebo, RU-28318, RU-486)
experimental design. Rats were treated for 28 days. Food intake and body
weight were monitored throughout the treatment period. At the end of the
treatment, rats were killed and their carcasses were analyzed for energy
and nitrogen contents. Energy content was determined by adiabatic bomb
calorimetry, whereas nitrogen was determined in 250-to 300-mg samples of
dehydrated carcasses, with the use of the Kjeldahl procedure. The energy as
protein was subtracted from total carcass energy to determine energy as
fat. The gains in energy, fat, and protein were calculated by subtracting
the values obtained at the end of the treatment period from initial values
estimated from the body weights measured at the beginning of the
experiment. A significant interaction effect of surgery and corticosteroid
antagonist was observed on body energy gain, energetic efficiency, and fat
gain. Whereas body energy gain, energetic efficiency, and fat gain were
larger in OVX rats than in sham-operated animals treated with either
placebo or RU-486, they were comparable in OVX and sham-operated rats
treated with RU-28318. Surgery, but not corticosteroid antagonist, had a
significant effect on digestible energy intake, energy expenditure, and
protein gain. All these variables were higher in OVX rats than in
sham-operated animals. Surgery also affected corticosterone levels and
adrenal weight. Both of these variables were lower in OVX rats than in
sham-operated animals. By demonstrating the ability of RU-28318 to
attenuate the effects of OVX on energy balance, the present study provides
evidence that MR occupation by corticosteroids facilitates the OVX-induced
changes in energy balance.
