Increase in ovarian kallikrein activity during ovulation in the gonadotrophin-primed immature rat
in ReproductionSummary. The ovulatory process was initiated in 25-day-old rats by injecting them with hCG (10 i.u., s.c.) 2 days after the animals had been primed with PMSG (10 i.u., s.c.). At 2-h intervals after hCG, the ovaries were extracted and assayed for glandular kallikrein activity by using a chromogenic substrate H-d-Val-Leu-Arg-p-nitroanilide) which exhibits optical density (at 405 nm) upon hydrolysis. In 0-h control ovaries the activity was 12·5 × 10−3 kallikrein units (KU)/mg protein and it increased to a peak of 56·6 × 10−3 KU/mg at 12 h after hCG, when the follicles first began to rupture. The kallikrein activity was distinguishable from ovarian plasminogen activator activity on the basis of pH optima and response to trypsin inhibitor (SBTI). The activity was inhibited by a s.c. dose of indomethacin of 0·3 mg/rat, or higher, and this dosage inhibited ovulation. The results suggest that kallikrein activity contributes to the degradation of Graafian follicles during ovulation in mammals.
Keywords: ovulation; kallikrein; plasminogen activator; indomethacin; rat
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