MEMBRANE-BOUND CARBOXYPEPTIDASE-M IS EXPRESSED ON HUMAN OVARIAN FOLLICLES AND CORPORA-LUTEA OF MENSTRUAL-CYCLE AND EARLY-PREGNANCY

We have previously reported that membrane-bound aminopeptidases were e xpressed on human follicles and corpora lutea (CL) and we showed that these aminopeptidases are involved in follicular growth, probably by r egulating extracellular peptide concentrations. in this study, the exp ression of membrane-bound carboxypeptidase-M (CP-M), which cleaves car boxyl-terminal amino acids from peptides extracellularly, on human fol licles and CL was examined. In growing and pre-ovulatory follicles, CP -M was immunohistochemically detected with weak or moderate intensity on theca interna cells. Although CP-M was not detected on granulosa ce lls in growing and pre-ovulatory follicles, it was strongly detected o n the cell surface of luteinizing granulosa cells isolated from patien ts undergoing in-vitro fertilization treatment, indicating that CP-M w as rapidly expressed on granulosa cells during ovulation. In menstrual and pregnant CL, CP-M was clearly detected on luteal cells. In menstr ual CL, the expression of CP-M mRNA was observed by reverse transcript ion-polymerase chain reaction (RT-PCR). Western blotting analysis reve aled that the molecular mass of the CP-M extracted from mid-luteal CL was 62 kDa. These results indicate that CP-M is a cell surface differe ntiation-related molecule of human granulosa, theca, and luteal cells. The rapid expression on granulosa cells during ovulation strongly sug gests the involvement of CP-M in the ovulation and CL formation proces ses.