HORMONAL-REGULATION OF MONOCYTE CHEMOATTRACTANT PROTEIN-1 MESSENGER-RIBONUCLEIC-ACID EXPRESSION IN CORPORA-LUTEA

Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that attracts monocytes and macrophages. It is known that macrophages accum ulate in the corpus luteum (CL) during luteal regression in many speci es. In this study, we investigated the regulation of MCP-1 mRNA in ovi ne and bovine CL during prostaglandin (PG)F-2 alpha-induced luteolysis , after LH treatment, or after pharmacologic activation of the protein kinase (PK) A or PKC intracellular effector systems. In experiment 1, ewes on day 11 or 12 of the estrous cycle were infused with saline or PGF(2 alpha). PGF(2 alpha) increased MCP-1 mRNA at 1 and 4 h after tr eatment. MCP-1 mRNA returned to basal level at 12 h and increased agai n at 24 h post treatment. In experiment 2, ewes received saline, PGF(2 alpha), phorbol 12-myristate 13-acetate (PMA), luteinizing hormone (L H), or forskolin infusion and CL were collected at 0 (untreated), 4, 1 2, or 24 h after infusion. Similar to experiment 1, PGF(2 alpha) induc ed MCP-1 mRNA at 4 and 24 h post treatment. PMA increased mRNA for MCP -1 at 4, 12, and 24 h. Treatment with LH or forskolin transiently decr eased MCP-1 mRNA expression. In experiment 3, cows were treated with a luteolytic dose (25 mg) of PGF(2 alpha) on day 4 or day 11 of estrous cycle and expression of MCP-1 mRNA was quantified. Steady-state conce ntrations of mRNA for MCP-1 were induced by PGF(2 alpha) treatment onl y in mid-cycle CL but not in early CL. In summary, administration of P GF(2 alpha) or activation of PKC induced MCP-1 mRNA expression. Expres sion of MCP-1 may be important for stimulating immune processes during luteal regression.