Immunocytochemical demonstration of steroid hormones in the granulosa cells of the medaka, Oryzias latipes.

Immunocytochemical identification of steroid hormones was performed in granulosa cells isolated from large ovarian follicles of the medaka. The granulosa cells recovered from daily spawning females, 8.5 h after the onset of light, reacted with anti-progesterone and anti-17 alpha-hydroxyprogesterone antibody, while the granulosa cells treated 2.5 h after the onset of light did not. After 6 h stimulation with gonadotropin (PMS) in vitro, the isolated granulosa cells reacted with anti-progesterone antibody. The granulosa cells examined 8.5 h after the onset of light did not react with anti-estradiol or anti-estriol antibody. These results demonstrate that, in Oryzias latipes, progestins (progesterone and 17 alpha-hydroxyprogesterone) are synthesized in the granulosa cells which are directly stimulated by gonadotropin.