Effect of A23187 or angiotensin II on ovarian metalloproteinase inhibitors and steroidogenesis in rats
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The present study examined the effect of the calcium ionophore A23187 or angiotensin II (AII) on the expression of ovarian metalloproteinase inhibitor and activity in rat granulosa cells and intact ovaries. Granulosa cells were collected from rats primed with pregnant mares' serum gonadotrophin (PMSG) and cultured for 24 h with A23187, AII, or the AII receptor antagonist, saralasin, in the presence or absence of LH. Metalloproteinase inhibitor activity and progesterone concentrations were determined in the media. In the A23187 experiment, addition of A23187 to granulosa cells, cultured without LH, decreased inhibitor activity, especially at the concentrations of 10 and 100 μmol l−1 (decrease to 33 ± 7% and 31 ± 5% of control culture values, respectively). Addition of LH to the media increased inhibitor activity 3.04 ± 0.39 times compared with the control; however, A23187 (10 and 100 μmol l−1), in the presence of LH, decreased inhibitor activity by approximately 67%. The ionophore had disparate effects on progesterone production. Without LH, A23187 increased progesterone production by 2.96 ± 0.47 times at 10 μmol l−1 and by 5.53 ± 0.65 times at 100 μmol l−1. However, in LH-stimulated cells, progesterone was inhibited by A23187 at 1 and 10 μmol l−1 but was unchanged at 100 μmol l−1. In the angiotensin experiment, addition of AII (0–10 000 nmol l−1) or saralasin (1 μmol l−1) did not affect inhibitor activity or progesterone concentrations compared with control values in the absence or presence of LH. For the angiotensin experiment in vivo, PMSG-primed rats were injected with hCG followed by saralasin (10 mmol l−1) 1 or 3 h later and killed at 4, 8, or 12 h after hCG. Expression of the ovarian tissue inhibitor of metalloproteinase-1 (TIMP-1) increased by 1.7 times at 4 h, 3.3 times at 8 h, and 3.0 times at 12 h after hCG compared with values in ovaries collected at the time of hCG injection. Administration of saralasin at 1 or 3 h after hCG had no effect on expression of TIMP-1 or on serum concentrations of progesterone or oestradiol. In summary, A23187 decreased granulosa cell-derived inhibitor activity, whereas AII had no effect. We propose that calcium may play a role in modulating proteolysis associated with ovulation, while AII does not appear to regulate ovarian metalloproteinase inhibitor activity.
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