Steroid hormone release in cultures of pig corpus luteum and granulosa cells: effect of LH, hCG, PRL and estradiol.

Porcine granulosa and luteum cells were isolated and cultured in vitro to compare their morphology and secretory activity with these of corpus luteum cells in vivo. Granulosa cells were isolated from preovulatory follicles and the luteal cells were collected from corpora lutea in the early or middle phase of the luteal cycle. The cells were grown as a monolayer for 8 days at 37 degrees C in the Parker's medium (M 199) supplemented with 10% of calf serum. The concentration of progestagens and estrogens in the medium was measured by the radioimmunological method [Abraham et al. 1971, Hotchkiss et al. 1971]. Both granulosa and luteal cells were cultured with the addition of following amounts of hormones: 100 ng LH, 600 ng hCG, 100 ng PRL and 150 ng estradiol per 1 ml of culture medium. At two days of culture the release of progesterone from granulosa cells significantly increased after the addition of 100 ng LH. Luteal cells isolated from the postovulatory corpus luteum released much higher amounts of progesterone than granulosa cells both in control cultures and in cultures supplemented with LH. A secretory stimulation of the luteal cells was observed only on the first day of culture irrespectively of the phase of the luteal cycle. In contrast, granulosa cells reacted by the elevation of hormonal release after the administration of hormones not only at the beginning of the culture, but also after several days. Prolactin did not stimulate the secretory activity of the granulosa cells and the same is valid for the cells isolated from the corpus luteum in the middle luteal phase. However, prolactin stimulated hormonal release of luteal cells isolated from the early corpus luteum.