Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that attracts monocytes and macrophages. It is known that macrophages accumulate in the corpus luteum (CL) during luteal regression in many species. In this study, we investigated the regulation of MCP-1 mRNA in ovine and bovine CL during prostaglandin (PG) F(2α)-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(2α). PGF(2α) increased MCP-1 mRNA at 1 and 4 h after treatment. MCP-1 mRNA returned to basal level at 12 h and increased again at 24 h post treatment. In experiment 2, ewes received saline, PGF(2α), phorbol 12-myristate 13-acetate (PMA), luteinizing hormone (LH), or forskolin infusion and CL were collected at 0 (untreated), 4, 12, 24 h after infusion. Similar to experiment 1, PGF(2α) induced MCP-1 mRNA at 4 and 24 h post treatment. PMA increased mRNA for MCP-1 at 4, 12, 24 h. Treatment with LH or forskolin transiently decreased MCP-1 mRNA expression. In experiment 3, cows were treated with a luteolytic dose (25 mg) of PGF(2α) on day 4 or day 11 of estrous cycle and expression of MCP-1 mRNA was quantified. Steady-state concentrations of mRNA for MCP-1 were induced by PGF(2α) treatment only in mid-cycle CL but not in early CL. In summary, administration of PGF(2α) or activation of PKC induced MCP-1 mRNA expression. Expression of MCP-1 may be important for stimulating immune processes during luteal regression.
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