Hormone-stimulated secretion of luteinization factor in porcine granulosa cells

Luteinization stimulator (LS) is an intrafollicular compound which was shown to be released by granulosa cells under in vitro conditions with stimulatory effects on immature granulosa cell differentiation. This study was undertaken to determine the effects of various endocrine agents which are involved in the regulation of ovarian function on LS secretion by porcine granulosa cells isolated from 5-8-mm follicles (LGC). Cell conditioned media (CM) obtained after the 4-day culture of LGC were tested in the culture of immature (small) granulosa cells (SGC). The activity of LS released into the LGC conditioned medium was estimated by measuring progesterone (P4) produced by SGC in the presence of CM. Stimulation of P4 secretion was observed after addition of media from cultures treated by LHRH (10(-4) mol.l-1), epinephrine (10(-5) mol.l-1), LH (1 microgram.ml-1), dbcAMP (0.5 and 2.0 micrograms.ml-1) or insulin (1.0-5.0 micrograms.ml-1). Norepinephrine (10(-5) and 10(-7) mol.l-1), estradiol (0.1 and 1.0 microgram.ml-1) and prolactin (0.1 and 1.0 microgram.ml-1) did not change steroidogenic activity of CM. Epinephrine and norepinephrine (10(-5) and 10(-7) mol.l-1), LH (1 microgram.ml-1), dbcAMP (2.0 microgram.ml-1) and estradiol (1 microgram.ml-1) alone enhanced P4 production by SGC, whereas LHRH (10(-3) and 10(-4) mol.l-1), insulin (1.0-5.0 microgram.ml-1) and prolactin (0.1 and 1.0 microgram.ml.-1) did not have any effect. These observations suggest that the process of LS secretion in developing follicles is subject to a specific hormonal control.