Effects of the phytoestrogen, genistein, and protein tyrosine kinase inhibitor-dependent mechanisms on steroidogenesis and estrogen receptor expression in porcine granulosa cells of medium follicles

The use of soy-based products in pig diets had raised concerns regarding the reproductive toxicity of genistein, the predominant isoflavone in soybeans. Genistein was reported to exhibit weak estrogenic activity but its mechanism of action is not fully recognized. The aim of the study was to examine the in vitro effects of genistein on (1) progesterone (P-4) and estradiol (E-2) secretion by porcine granulosa cells harvested from medium follicles, (2) the viability of cultured granulosa cells, and (3) the mRNA and protein expression of estrogen receptors alpha and beta (ER alpha and ER beta) in these cells. In addition, to verify the role of protein tyrosine kinase (PTK)-dependent mechanisms possibly involved in genistein biological action, we tested the effects of lavendustin C, the nonsteroidal PTK inhibitor, on granulosa cell steroidogenesis. We found that genistein inhibited (P < 0.05) basal P-4 secretion by granulosa cells harvested from medium follicles of pigs. In contrast, lavendustin C did not affect basal P-4 secretion by the cells. Moreover, genistein increased (P < 0.05) basal granulosal secretion of E-2. In contrast, lavendustin C did not alter basal E-2 secretion by porcine granulosa cells. In addition, we demonstrated that genistein increased mRNA and protein expression of ER beta (P < 0.05) in the examined cells. The expression of ER alpha mRNA was not affected by genistein and ER alpha protein was not detected in the cultured granulosa cells of pigs. In sturinnary, the genistein action on follicular steroidogenesis in pigs involved changes in the granulosal expression of ER beta. However, the genistein action on P-4 and E-2 production by granulosa cells harvested from medium follicles did not seem to be associated with PTK. (C) 2013 Elsevier Inc. All rights reserved.