INHIBITION OF MULLERIAN INHIBITING SUBSTANCE SECRETION BY FSH

To evaluate the role of gonadotropins in the control of Mullerian Inhibiting Substance (MIS) secretion, pregnant rats were injected with rabbit antiserum against luteinizing hormone releasing hormone (LHRH), and their pups replaced with follicle stimulating hormone (FSH) and human chorionic gonadotropin (hCG). The LHRH antiserum (LHRH-AS) was given at 13 and 20 days of gestation. Control dams were injected with an equal volume of normal rabbit serum. The male pups from mothers treated with LHRH antiserum were given 5 daily s.c. injections of the FSH, hCG, or vehicle. The male pups from mothers treated with normal rabbit serum were given vehicle s.c. Testicular fragments of 6 day old pups born to mothers treated with LHRH antiserum during pregnancy showed an increase relative to controls in MIS activity in a graded organ culture bioassay system (grade 3.4 ± 0.3 vs. 2.3 ± 0.2) (P < 0.01). FSH given to pups from mothers treated with LHRH antiserum reduced testicular MIS secretion compared to vehicle treated pups from the same mothers (grade 2.3 ± 0.2 vs. 3.4 ± 0.3) (P < 0.01). Thus, postnatal injections of FSH after immunologic blockade of gonadotropins in utero reduced MIS activity of the testes to the same level found in testes of 6 day control pups (grade 2.3 ± 0.2 vs. 2.3 ± 0.2). In contrast, MIS activity remained high despite postnatal hCG injection in pups born to mothers given LHRH-AS (grade 3.4 ± 0.4 vs. 3.4 ± 0.3). These studies suggest that secretion of MIS is dependent on normal hypothalamic secretion of LHRH and may be inhibited by FSH. © 1979 International Pediatric Research Foundation, Inc.