Effects of adrenocorticotrophic hormone on the expression of matrix metalloproteinases and their inhibitors in the bovine ovary.

Cattle undergo numerous environmental and management stressors that reduce fertility and affect ovulation. The extracellular matrix of the follicle wall can be altered by matrix metalloproteinases (MMPs), the activities of which are regulated by interleukins and tissue-specific inhibitors of metalloproteinases (TIMPs), especially during ovulation. The aims of the present study were to: (1) evaluate changes in the hormone milieu, the localisation and activity of MMP2 and MMP9 and the localisation of MMP14, TIMP1 and TIMP2 in response to adrenocorticotrophic hormone (ACTH) during the preovulatory period in cows; and (2) determine the direct effects of ACTH on the mRNA expression of MMP2 and MMP9 in the cultured follicle wall of bovine ovaries obtained from an abattoir. 100IU ACTH was administered during pro-oestrus every 12h until ovariectomy, which was performed before ovulation. Cortisol concentrations in the plasma and follicular fluid (FF) of preovulatory follicles were higher in ACTH-treated than control cows. Progesterone presented subluteal concentrations in plasma of ACTH-treated cows (P<0.05). MMP2 immunostaining and activity in ovaries were higher in ACTH-treated than control cows (P<0.05), whereas MMP9 immunostaining was similar between the two groups. However, unlike in control cows, MMP9 activity was absent in the FF of ACTH-treated cows. These results suggest that the administration of ACTH during the preovulatory period in cows could cause changes that culminate in modifications in the content and activation of MMPs and TIMPs in the ovary, which could interfere with the ovulation process.