Regulation of prostaglandin synthesis by progesterone in the bovine corpus luteum

The objective of the present study was to investigate the influence of progesterone on prostaglandin synthesis by the corpus luteum (CL). Corpora lutea were obtained from dairy cows on days 4, 6, 10, and 18 of the estrous cycle, dissociated, and placed in serum-free culture. The addition of luteinizing hormone (LH) resulted in a slight, but non-significant (p greater than 0.05), increase in levels of 6-keto-PGF1 alpha, and had no effect on PGF2 alpha. Progesterone treatment caused a significant, dose-dependent decrease in both PGF2 alpha and 6-keto-PGF1 alpha in 6-day and 10-day corpora lutea, but not in 4-day or 18-day corpora lutea. In the 6- and 10-day corpora lutea, progesterone treatment resulted in a greater inhibition of PGF2 alpha than 6-keto-PGF1 alpha production. Therefore, progesterone treatment brought about an increase in the 6-keto-PGF1 alpha to PGF2 alpha ratio in these cells (12.9 vs. 21.3). It is concluded from these studies that progesterone can modulate luteal prostacyclin and PGF2 alpha synthesis, suggesting an interaction of progesterone and prostaglandin production within the corpus luteum.