We have recently shown that not only bradykinin, but also all components for the production of bradykinin, can be detected within the follicle of porcine ovaries. To elucidate the relevance of the intrafollicular bradykinin-producing system to its physiological role, we investigated the distribution of bradykinin receptor (B₂R) mRNA and the protein in porcine ovaries. A cDNA encoding porcine B₂R was first cloned from a porcine uterus cDNA library. The receptor mRNA was scarcely detected in the ovary by Northern blot analysis. Polymerase chain reaction analysis with total RNAs isolated from the ovary and from granulosa cells of small and large follicles demonstrated the ovarian expression of B₂R mRNA. The B₂R protein was detected by Western blot analysis in extracts of isolated granulosa cells. In situ hybridization of B₂R mRNA and immunohistochemical analysis of the protein revealed that the receptor is expressed in the theca and granulosa cells of all growing follicles. The effect of bradykinin on the expression of some matrix metalloproteinase (MMP) genes was examined using isolated granulosa cells. Bradykinin treatment induced MMP-3 and MMP-20 gene expression to an extreme degree. The expression of MT1-MMP was also affected by bradykinin treatment. These results suggest that MMPs play a role in follicle rupture during ovulation. The present study provides new information regarding the mechanisms of bradykinin-induced ovulation in porcine ovaries.