Release of progesterone by porcine luteal cells from different days of estrous cycle: effect of LH, PRL and PGF2 alpha.

The secretion of progesterone (P4) by porcine luteal cells from 5th, 8th, 14-16th and 17th day of estrous cycle was estimated under basal conditions and after stimulation with LH (0.1 and 1 microgram ml-1), PRL (2 micrograms ml-1) and PGF2 alpha (0.1 and 5 micrograms ml-1). P4 in the medium was estimated by radio-immunological method after 30 min and then after 3, 6, 9 and 15 h of incubation. Luteal cells from 5th, 8th, 13th, 14-16th and 17th day of estrous cycle released on average 140.9 +/- 14.4, 138.9 +/- 12.7, 224.4 +/- 21.3, 62.3 +/- 4.2 ng and 6.4 +/- 0.6 ng P4 per ml-1 medium, respectively. Luteal cells from 5th day of the estrous cycle significantly increased (P less than 0.05) P4 release during first 30 min of incubation in the presence both doses of LH, but the dose of 1 microgram LH significantly stimulated P4 secretion during next 3 h, too. Only the luteal cells from 13th day of the estrous cycle increased (P less than 0.05) P4 production in the presence of 1 microgram LH, and prolactin exerted luteolytic effect also only on luteal cells from 13th day of the estrous cycle. The release of P4 by luteal cells from 5th day of the estrous cycle increased (P less than 0.05) during first 30 min of incubation in the presence of PGF2 alpha. However, PGF2 alpha (5 micrograms) exerted inhibitory effect (P less than 0.05) on P4 release by luteal cells from only 13th day of the estrous cycle. The results showed that the effect of these hormones on P4 secretion by luteal cells depended on the period of estrous cycle and doses used.