The matrix metalloproteinases (MMPs) play critical roles in the ovulatory process. Their expression and activity, together with those of the endogenous tissue inhibitors of metalloproteinases (TIMPs), are stimulated by LH. The LH surge initiates a cascade of events resulting in ovulation and formation of the corpus luteum via activation of protein kinases A and C, as well as tyrosine kinases. In vitro perfused rat ovaries were untreated, or treated with LH (0.2 microg ml(-1)) plus 0.2 mmol 3-isobutyl-1-methylxanthine l(-1) with 0, 10 or 100 micromol genistein l(-1) (an inhibitor of tyrosine kinases) to assess whether tyrosine kinases are mediators of the LH-stimulated increase in ovarian expression of the MMPs and TIMPs. After 10 h of perfusion, ovaries were collected and frozen until RNA isolation. Northern and RNase protection analyses were used to measure mRNA encoding collagenase 3, gelatinases A and B, and TIMPs-1, -2 and -3. Treatment with LH plus 3-isobutyl-1-methylxanthine resulted in a two- and fivefold increase in mRNA encoding collagenase 3 and TIMP-1, respectively (P < 0.05). Treatment with 100 micromol genistein l(-1) blocked the LH-stimulated increase in collagenase 3 (0.012 +/- 0.002 versus 0.028 +/- 0.005 relative units for 100 micromol genistein l(-1) versus LH; P < 0.05), whereas neither dose of genistein affected LH-induced TIMP-1 expression. LH alone or with genistein did not alter the expression of mRNA encoding TIMP-2 and TIMP-3, or mRNA encoding gelatinases A and B. These data indicate that tyrosine kinases play a role in the LH-induced tissue remodelling required for ovulation by mediating the LH-stimulated expression of collagenase 3.