The conversion of androgen to estrogen is mediated by aromatase activity, and 19-hydroxylase and C10-19lyase are seen to be involved in C19-demethylation. The present study is to demonstrate C10-19lyase activity in adrenal tissue. Fetal bovine and pig adrenal tissue homogenates were incubated with14 C-androstenedione (A) and NADPH under air. The products 14C-19-OHA, 14C-19-norA, with added carrier standard 3H-19-OHA, 3H-19-norA were separated and purified by T. L. C.. The identification of 19-norA was established by recrystallization and that of 19-OHA by C. C. D.. The 3H/14C ratios of the products 19-norA were found to be constant in repeated crystallization. The amount of 19-OHA from A in fetal adrenal tissue was 30.0nmol/h/g protein, and that of 19-norA from A was 12.59pmol/h/g protein. C10-19lyase activity from 19-OHA, calculated by the amounts of 19-norA in fetal, bovine and pig adrenal tissue, was 49.7, 3.50, 10.3pmol/h/g protein, respectively. This is the first report to demonstrate androgen C10-19lyase in human fetal adrenal tissue, and it is assumed that fetal adrenal tissue forms 19-norA via 19-OHA.
