Progesterone production in vitro by mouse luteal cells: response to follicle-stimulating hormone, luteinizing hormone, and prolactin.

The purpose of this study was to determine the effects of ovine follicle-stimulating hormone (FSH), luteinizing hormone (LH); prolactin, and recombinant FSH and a protein kinase C activator (phorbol 12-myristate 13-acetate [PMA]) on progesterone production by dispersed luteal cells (large + small) from Day 4 pregnant mice. Corpora lutea (CL) were collected on Day 4 of pregnancy (Day 1 = sperm positive smear), and dispersed luteal cells were isolated using collagenase. After overnight incubation, the luteal cells were incubated with or without FSH, LH, prolactin, or recombinant human FSH or PMA for 4 hr or an additional 24 hr at 37 degrees C; media were collected and progesterone was determined by RIA. Ten nanograms and 100 ng of ovine FSH, LH and prolactin were all equally effective in stimulating progesterone synthesis in media recovered after 24 hr of incubation. Moreover, the combination of all three gonadotropins yielded maximum levels of progesterone indicating a luteotrophic complex in vitro, paralleling previous in vivo findings. Recombinant human FSH-devoid of LH contamination-at doses of 10 and 100 ng also significantly stimulated progesterone synthesis, which strongly suggests that FSH has luteotropic activity in the mouse, thus agreeing with our previous in vitro results with CL of the pregnant hamster and rat. One hundred nanomolar PMA by itself did not affect progesterone production but significantly decreased dibutyrl cAMP-, forskolin-, FSH-, and LH-induced progesterone production, suggesting that activation of protein kinase C may block the luteotropic effects of LH and FSH during murine pregnancy.