Prostacyclin, Prostaglandin F2 a and Progesterone Production by Bovine Luteal Cells During the Estrous Cycle’

Corpora lutea (CL) were collected from Holstein heifers on Days 5, 10, 15 and 18 (5/day) of the estrous cycle. Dispersed lutes! cell preparations were made and 106 viable lutes! cells were incubated with bovine lutemnizing hormone (LH) and different amounts of arachidonic acid in the presence and absence of the prostaglandin (PG) synthetase inhibitor indomethacin. The concentra-tions of progesterone, PGF2a and 6-keto-PGF1a, the stable inactive metabolite of prostacyclin (PGI2), were measured. Day 5 CL had the greatest initial content of 6-keto-PGF1o (1.01 ± 0.16 ng/10 ’ cells), and synthesized more 6-keto-PGF1a (2.55 ± 0.43) than CL collected on Days 10 (0.57 ± 0.11), 15 (0.08 ± 0.05) and 18 (0.19 ± 0.03) during a 2-h incubation period. Arachidonic acid stimulated the production of 6-keto-PGF1a by Days 10, 15 and 18 lutes! tissue. PGF2a was produced at a greater rate on Day 5 (0.69 ± 0.17 ng/10 ’ cells) than on Days 10 (0.06 ± 0.01), 15 (0.04 ± 0.02) and 18 (0.08 ± 0.01). Arachidonic acid stimulated and indometha-cm inhibited the production of PGF2a, in most cases. The initial content of 6-keto-PGF1a was higher than that of PGF2a on all days of the cycle and more 6-keto-PGF1n was synthesized in response to arachidonic acid addition. The ratio of 6-keto-PGF1 a content to PGF2a content was 4.39, 2.30, 1.25 and 1.13 on Days 5, 10, 15 and 18, respectively. Progesterone production during the 2-h incubation decreased as the age of the CL advanced and the concentration of PCI2 declined. Concentrations (ngIIO6 cells) were 128 ± 12, 87 ± 18, 38 ± 9 and 54 ± 7 on Days 5, 10, 15 and 18, respectively. These data and others suggest that PGI2 may play an important luteotropic role, particularly during the first 10 days of the bovine estrous cycle