Luteoprotective Mechanisms of Prostaglandin F2α Stimulated by Luteinizing Hormone in the Bovine Corpus Luteum

Luteinizing hormone (LH) regulates several ovarian functions. However, the luteoprotective mechanisms of LH involved in the maintenance of bovine corpus luteum (CL) function are not well understood. Since prostaglandin F2α (PGF), PGE2 and progesterone (P4) are well documented as antiapoptotic factors in the bovine CL, we hypothesized that LH protects the CL by stimulating the local production and action of PGF, PGE2 and P4. Cultured bovine luteal cells obtained at the mid-luteal stage (days 8-12 of the estrous cycle) were treated with LH (10 ng/ml), onapristone (OP: a specific P4 receptor antagonist, 100 μM) and indomethacin [INDO; a cyclooxygenase (COX) inhibitor, 100 μM] for 24 h. LH with and without OP significantly increased the mRNA and protein expressions of COX-2, PGF synthase and carbonyl reductase (P<0.05) but not the mRNA and protein expressions of COX-1 and PGE synthase in bovine luteal cells. In addition, these treatments significantly increased PGF and P4 production (P<0.05) but not PGE2 production. Luteal cell viability was significantly increased by LH alone (P<0.05), but LH-increased cell viability was reduced by LH in combination with INDO as well as OP (P<0.05). The overall results suggest that LH prevents luteal cell death by stimulating luteal PGF and P4 production and supports CL function during the luteal phase in cattle.