Sex Differences in Adrenal Cortical Secretion in the Rat1

Ether anesthesia administered as a standardized stress produced higher and more persistently elevated plasma corticosterone concentrations in female rats than in male animals. Similar effects were obtained following administration of ACTH. The biological half-life of corticosterone in female rats was found to be 13 minutes compared to 20 minutes in male animals. Female rat liver homogenates metabolized the A ring of corticosterone and that of cortisone more rapidly in vitro than did male tissue. No sex difference was observed in the rate of metabolism of the sidechain of corticosterone although male liver homogenates reduced the sidechain of cortisone more rapidly than did female tissue. The concentration of corticosterone in the adrenal vein of the female rat is 2.5 times that in the male. These findings are interpreted to signify increased sensitivity of the female adrenal gland to stimulation by ACTH. The higher plasma corticosterone levels observed after ACTH or stress in female rats are not explained by the sex differences in the rate of clearance and metabolism of the steroid. An additional possibility to be considered is that the female pituitary gland is more responsive to stress with respect to ACTH release.