In vitro effects of genistein and daidzein on the activity of adrenocortical steroidogenic enzymes in mature female pigs.

Soy products, commonly used as a protein source in farm animals' diets, contain considerable quantities of non-nutrient constituents such as phytoestrogens. Genistein and daidzein are known to affect the reproductive processes in humans and animals. However, reports concerning phytoestrogens and porcine adrenal steroidogenesis are scarce, and the adrenal mechanism of phytoestrogen action in species other than humans and rodents is poorly recognized. The goal of the present paper was to examine the in vitro effects of genistein and daidzein on the activity of key enzymes for cortisol and corticosterone synthesis in porcine adrenocortical cells harvested during the luteal or follicular phase of the porcine estrous cycle. The cells were treated with genistein or daidzein (10 μM), with or without ACTH (5 nM), in the presence or absence of precursors (1 μM) of cortisol (pregnenolone, P5; progesterone, P4; 17-hydroxyprogesterone, 17OH-P4; or 11-deoxycortisol, 11d-cortisol) or corticosterone: (P5 or P4) synthesis. The supplementation of a medium with P5, P4, 17OH-P4 or 11d-cortisol enabled us to measure the activity of cholesterol side-chain cleavage enzyme (P450scc), 3β-hydroxysteroid dehydrogenase (3β-HSD), 17α-hydroxylase/C17-20 lyase (P450c17) or 21-hydroxylase (P450c21) and 11β-hydroxylase (P45011β), respectively. We demonstrated that in sexually mature, cyclic pigs, regardless of the phase of the estrous cycle, phytoestrogens genistein and daidzein suppressed basal and ACTH-stimulated in vitro secretion of cortisol and corticosterone via progesterone synthesis inhibition. This indicates that phytoestrogens specifically inhibit the 3β-HSD activity in porcine adrenocortical cells. We suggest that genistein and daidzein present in soy products may negatively affect glucocorticoid synthesis of mature gilts by disrupting adrenal steroidogenesis at the 3β-HSD level.