SEX DIFFERENCE IN THE RATE OF DISAPPEARANCE OF CORTICOSTERONE-4-C14FROM PLASMA OF INTACT RATS: FURTHER EVIDENCE FOR THE INFLUENCE OF HEPATIC Δ4-STEROID HYDROGENASE ACTIVITY ON ADRENAL CORTICAL FUNCTION1

Abstract

The half-time for the disappearance of corticosterone from plasma in female rats is much shorter than that in males. This large sex difference in steroid metabolism in vivo corresponds to the in vitro sex difference in corticosteroid inactivation by hepatic Δ⁴-steroid hydrogenases, but is opposite to the sex difference in cortisone metabolism by hepatic C20-carbonyl hydrogenases. From calculations based on these data we conclude that the half-life is ordinarily independent of hepatic blood flow. The steady-state rate of corti-costerone secretion was estimated in both sexes. Under the conditions of these experiments the female adrenal cortex appears to secrete corticosterone in vivo at a steady-state rate more than twice as great as that of male adrenals. The virtual volume of distribution and the half-life of corticosterone both appear to be independent of the dose of corticosterone administered, over a four-fold physiological concentration range.