A comparison of the effects of cyclooxygenase prostanoids on progesterone production by small and large bovine luteal cells.

Highly purified preparations of small and large bovine luteal cells were utilized to examine the effects of prostaglandins F2 alpha (PGF2 alpha), E2 (PGE2) and I2 (PGI2) analog on progesterone production. Corpora lutea were obtained from Holstein heifers between days 10 and 12 of the estrous cycle. Purified small and large cells were obtained by unit gravity sedimentation and flow cytometry. Progesterone accumulation was determined in 1 x 10(5) small and 5 x 10(3) large cells after 2 and 4 h incubations respectively. Progesterone synthesis was increased (p less than 0.05) in the small cells by the increasing levels of PGF2 alpha, PGE2, carba-PGI2 and LH. PGF2 alpha, but not PGE2 or carba-PGI2 increased (p less than 0.05) LH-stimulated progesterone production. There was no interaction of various combinations of prostaglandins on progesterone production in the small cells. In the large cells, PGF2 alpha had no effect on basal progesterone production. However, it inhibited LH-stimulated progesterone synthesis. In contrast, PGE2 and carba-PGI2 stimulated (p less than 0.05) basal progesterone production in the large cells. In the presence of LH, high levels of carba-PGI2 inhibited (p less than 0.05) progesterone synthesis. The PGE2 and PGI2-stimulated progesterone production in the large luteal cells was also inhibited in the presence of PGF2 alpha. These data suggest all of the prostaglandins used exert a luteotropic action in the small cells. In the large cells only PGE2 and carba-PGI2 are luteotropic, while PGF2 alpha exerts a luteolytic action. The effects of the prostaglandins in the small and large luteal cells suggest that their receptors are present in both cell types.