KALLIKREIN GENE FAMILY EXPRESSION IN THE RAT OVARY - LOCALIZATION TO THE GRANULOSA-CELL

The glandular or tissue kallikreins are a multigene family of serine p roteases, of which 13 genes (rKLK1-13) have been identified in the rat and are expressed in a wide variety of tissues. Kallikrein-like enzym e activity has been detected during the periovulatory period in the go nadotropin-primed immature female rat ovary and suggested to play a ro le in the inflammatory-like response at ovulation. In this study, we e xamined whether this enzyme activity was due to local expression of a rat KLK gene family member. Ovarian RNA, prepared from gonadotropin-tr eated animals, was assessed for rKLK gene expression by reverse transc riptase-polymerase chain reaction (RT-PCR) with universal rKLK primers derived from highly conserved regions in the rat KLK genes. Southern blot analysis of the RT-PCR products, using oligonucleotide probes spe cific for the individual genes, indicated that five rKLK gene family m embers, rKLK1 (encoding true kallikrein), rKLK3, rKLK7, rKLK8, and rKL K9, were expressed at varying levels in the ovaries of both untreated control and gonadotropin-treated immature female rats. The identities of these five rKLK messenger RNAs were further confirmed by DNA sequen ce analysis of the PCR products. In situ hybridization of gonadotropin -treated ovaries localized rKLK3 and rKLK7 gene expression to the lute inizing granulosa cells of periovulatory follicles. In an enriched pop ulation of nonluteinizing granulosa cells prepared from estrogen-prime d animals, we also demonstrated rKLK3, rKLK7, rKLK9, and rKLK12 (but n ot rKLK1 or rKLK8) expression, whereas all six genes were expressed in the ovaries of these animals. In summary, we have reported the expres sion of six KLK gene family members in the rat ovary and localized thi s expression primarily to the granulosa cell. The potential roles of t hese enzymes in ovulation or other aspects of ovarian, particularly gr anulosa cell, function are yet to be elucidated.