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

Abstract

Highly purified preparations of small and large bovine luteal cells were utilized to examine the effects of prostaglandins F 2 α(PGF 2 α), E 2 (PGE 2) and I 2 (PGI 2) 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 × 10 5 small and 5 × 10 3 large cells after 2 and 4 h incubations respectively. Progesterone synthesis was increased (p<0.05) in the small cells by the increasing levels of PGE 2 α, PGE 2, carba-PGI 2 and LH. PGF 2α, but not PGE 2 or carba-PGI 2 increased (p<0.05) LH-stimulated progesterone production. The was no interaction of various combinations of prostaglandins on progesterone production in the small cells. In the large cells, PGF 2 α had no effect on basal progesterone production. However, it inhibited LH-stimulated progesterone synthesis. In contrast, PGE 2 and carba-PGI 2 stimulated (p<0.05) basal progesterone production in the large cells. In the presence of LH, high levels of carba-PGI 2 inhibited (p<0.05) progesterone synthesis. The PGE 2 and PGI 2-stimulated progesterone production in the large luteal cells was also inhibited in the presence of PGF 2 α. These data suggest that all of the prostaglandins used exert a luteotropic action in the small cells. In the large cells only PGE 2 and carba-PGI 2 are luteotropic, while PGF 2 α 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.