THE RELATIONSHIP BETWEEN CORTICOSTERONE SYNTHESIS FROM ENDOGENOUS PRECURSORS AND FROM ADDED RADIOACTIVE PRECURSORS BY RAT ADRENAL TISSUE IN VITRO

Abstract

SUMMARY: A kinetic study of corticosterone recovered during incubation of rat adrenal tissue with [4-¹⁴C]progesterone and [16-³H]pregnenolone shows that both its ³H: ¹⁴C ratio and its specific activity change with time throughout incubation. Corticosterone is itself metabolized, and hypotheses based on the rate of production of corticosterone may be therefore deceptive when the amount is measured at a single point in time. Thus disparities between the specific activities of products and intermediates may be expected which alone do not necessarily indicate differences between the biosynthetic pathways involved in production from endogenous precursors and those from added radioactive precursors. Other experiments suggest that steroids in incubation media, in concentrations comparable with those found in adrenal venous plasma, do not inhibit the continued synthesis of hormones.