Stimulation of matrix-metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 gene expression in rats by the preovulatory prolactin peak

Department of Obstetrics and Gynecology, Division of Clinical and Experimental Endocrinology, University of Gottingen, Gottingen, Germany.

Since structural luteolysis involves deterioration of tissue, the gene expression of matrix-metalloproteinase-1 (MMP-1) and the respective tissue inhibitor of this metalloprotease (TIMP-1) were measured at various times on the day of pro-oestrus and in animals in which the preovulatory prolactin surge was blocked for the duration of 3 cycles by bromocriptine. An additional group of prolactin-blocked rats received a prolactin replacement injection on the afternoon of pro-oestrus. In spontaneously pro-oestrous rats, MMP-1 and TIMP-1 gene expression increased significantly (P<0.01) prior to the occurrence of the preovulatory LH surge but simultaneously with the onset of the preovulatory prolactin surge. When prolactin release was blocked by bromocriptine for 3 cycles, no such changes were observed during the afternoon of pro-oestrus. However, an intraperitoneal injection of bovine prolactin at the time when the preovulatory prolactin surge occurs normally, increased MMP-1 and TIMP-1 gene expression (P<0.01). These results indicate that MMP-1 and TIMP-1 gene expression are stimulated by the preovulatory prolactin surge. Previous work has shown that the preovulatory LH surge activates the enzymatic cascade which leads to increased collagenase activity.

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