Effects of ovariectomy on dexamethasone suppression of the adrenal axis in adult rats.
Three weeks after ovariectomy, adult female rats had lower basal levels of serum corticosterone (B), which did not display a daily rhythm, and reduced responses to ether stress, measured by blood levels of B 15 min after ether exposure. Ovariectomized (OVX) females were more sensitive to dexamethasone (DEX) suppression of the ether induced stress response, reaching basal levels at a dose of 50 mug DEX/100 g b.w. At this dose, B levels were reduced by only 30% over saline-control values in intact rats. DEX-treated intact rats displayed a short-term suppression, reaching a maximum 2 h after the injection followed by a rebound 7 h post-injection and a second suppression period evident by 11 h post-injection. OVX rats showed a steadily increasing suppression that began 1 h after injection and persisted to the last sample time at 11 h post-injection. The disappearance of DEX from peripheral blood was followed by means of radioimmunoassay and no difference was found between intact and OVX rats either in the basal state or 15 min after ether stress. It can be concluded that ovarian steroids condition the sensitivity of the adrenal axis to DEX suppression and that the differences in DEX sensitivity  we have previously noted between prepubertal and adult rats can be accounted for by a change in gonadal status rather than by a critical developmental event in the adrenal axis itself.
D000311:Adrenal Glands / Q000502:physiology; D000818:Animals; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood*; D003907:Dexamethasone / Q000097:blood / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004986:Ether; D005260:Female; D010053:Ovary / Q000502:physiology*; D051381:Rats; D013312:Stress, Physiological / Q000097:blood* / Q000139:chemically induced; D013997:Time Factors
D004986:Ether; D003907:Dexamethasone; D003345:Corticosterone