The objective of this proposal is to investigate the mechanism by which testicular androgen induces the fetal mouse genital tract differentiation. During the last few, years, we made some observations which suggest that fetal androgen after binding to its receptor induces the synthesis of phospholipase stimulatory protein(s) resulting in stimulation of phospholipase A2 (PLA2). This, in turn, induces the arachidonic acid release leading to increased synthesis of prostaglandin E2 (PGE2). Consequently, masculine differentiation is induced. We plan to investigate this hypothesis further by determining specific roles of different intermediates of the above-mentioned pathway, namely, PGE2, PLC and phospholipase A2-stimulatory proteins (PLSP). Thus, we propose (1) to investigate whether a direct exposure of a PG depriving agent, namely, indomethacin, in an in vitro organ culture system results in the complete prevention of the androgen-induced masculinization i.e. disruption of the differentiation of internal genitalia, which was not observed with the indirect in vivo exposure; (2) to investigate whether PGE2 modulates ornithine decarboxylase to induce the differentiation; (3) to determine whether induction of PLC during the differentiation results in an induction of diacylglycerol and inositol triphosphate, the cell proliferating system; (4) to identify and characterize the PLA2-stimulatory and masculinizing activities of male PLSP using polydonal and monoclonal antibodies prepared against the protein(s) with these activities; (5) to investigate the difference between male and female PLSP, and (6) to determine the synthesis and localization of PLA2-stimulatory and masculinizing proteins during the genital tract differentiation of males and females.