Effects of TPA, A23187, and prostaglandin F2 alpha on progesterone synthesis by dispersed ovine luteal cells

The possible roles of protein kinase C, intracellular calcium, and oxygen environment in luteal progesterone (P4) production and their interaction with prostaglandin (PGF2 alpha) were investigated in dispersed ovine luteal cells. The following experiments were performed: 1) dose response to TPA and A23187, 2) interactions between the phorbol ester TPA and PGF2 alpha at 5% or 18% O2, 3) effect of TPA and PGF2 alpha on basal and luteinizing hormone (LH)-stimulated P4 secretion, 4) interaction of submaximal inhibitory concentrations of TPA with PGF2 alpha and the effect of indomethacin (IN) on the TPA response. Day 9 (Day 0 = first day of estrus) corpora lutea (CL) from ewes exhibiting estrous cycles of normal duration (15-17 days) were dispersed and 50,000-150,000 cells were cultured for 4 h in Dulbecco's Modified Eagle Medium. The proportion of luteal cells greater than 22 microns in diameter in these preparations averaged 17.8 +/- 2.1%. P4 in medium and cells was measured by radioimmunoassay. Both TPA and A23187 inhibited basal P4 accumulation in a dose-dependent manner. Maximum inhibition (500 nM) by TPA was greater than by A23187 at the same concentration (66.4 +/- 3.4 and 83.2 +/- 7.2% of controls, respectively; p less than 0.05), and the two were not additive in their effects. Reducing O2 did not affect P4 accumulation with or without TPA, PGF2 alpha, or both. Basal P4 accumulation was inhibited 30% by TPA and 10% by PGF2 alpha, but no additivity was seen.(ABSTRACT TRUNCATED AT 250 WORDS)