Steroid synthesis in the adrenal gland of the sea snake Hydrophis cyanocinctus: The metabolism of exogenous precursors

Sea snake (Hydrophis cyanocinctus) adrenal glands (whole homogenates, preincubated minces, or mitochondrial preparations) were incubated in vitro with exogenous radioactive precursors. Hydrophis adrenal tissue was capable of synthesizing 17-deoxycorticosteroids from exogenous cholesterol, pregnenolone, progesterone, and DOC, but not from sodium [¹⁴C]-acetate. Products identified after incubation were pregnenolone, progesterone, 11β-hydroxyprogesterone, DOC, corticosterone, 18-hydroxycorticosterone, and aldosterone. The major product was corticosterone with lesser quantities also of 18-hydroxycorticosterone and aldosterone. In the case of the mitochondrial preparation 11β-hydroxyprogesterone predominated. No evidence for the biosynthesis of cortisol from cholesterol was found. Two types of kinetic incubation were employed: One sampled the incubation medium alone, while the other sampled both medium plus tissue. It was concluded that sampling the medium only did not allow the identification of the biosynthetic pathways operating in vitro. However, from sampling both the medium and the tissue it was concluded that both the C21-C11 and C11-C21 sequences of hydroxylation operated in the conversion of progesterone to corticosterone. The data contrast with those obtained from previous studies on cobra adrenal tissue, particularly with regard to the ability of sea snake adrenals in vitro to 18-oxygenate exogenous precursors.