PURIFIED HUMAN ALPHA-FETOPROTEIN INHIBITS FOLLICLE-STIMULATING HORMONE-STIMULATED ESTRADIOL PRODUCTION BY PORCINE GRANULOSA-CELLS IN CULTURE

We have investigated the effects of purified alpha-fetoprotein (AFP) o n follicle-stimulating hormone (FSH)-stimulated estradiol production b y porcine granulosa cells in monolayer culture. Granulosa cells isolat ed from small follicles of prepubertal pigs were cultured for 2 days i n 5% fetal bovine serum for attachment and incubated for 3 days in med ium containing androstenedione and various treatments. The media were then collected and assayed for estradiol by radioimmunoassay. Human AF P significantly (P < 0.05) and dose-dependently inhibited FSH-stimulat ed estradiol production with 313 ng/ml AFP returning FSH-stimulated es tradiol to basal levels; human serum albumin was without effect. AFP p urified from either term cord blood or midtrimester amniotic fluid dos e-dependently inhibited estradiol production stimulated by the combina tion of FSH and insulin-like growth factor-I. Furthermore, 125 ng/ml A FP inhibited estradiol production stimulated by cholera toxin, forskol in and cAMP. In contrast, extracellular accumulation of cAMP and proge sterone production was not inhibited by AFP. These data indicate that physiological concentrations of purified AFP significantly and dose-de pendently inhibit FSH-stimulated estradiol production by porcine granu losa cells in culture. Since AFP is known to augment growth factor-med iated cell growth, these data suggest that AFP inhibits differentiated functions (such as aromatase) while enhancing the proliferation of po rcine granulosa cells.