Immunoneutralization of inhibin suppresses reproduction in female mink

Abstract

This study determined whether immunoneutralization of inhibin affected gonadotropin secretion, embryo development, and ovarian function in mink. Adult female mink (n = 10) were immunized with bovine inhibin alpha1-26 gly-tyr (bINH, 100 μg) conjugated to human alpha globulins (HAG), or with HAG alone (n = 10, controls), mixed with Freund's complete adjuvant. A series of five boosters containing bINH or HAG were then administered during a 2-yr period. Titers of bINH antibodies and serum concentrations of gonadotropins were determined for each breeding season in 1990 and 1991. Each year after whelping, we determined gestation length; sex, number, and weight of live and dead kits per litter at birth; and number and weight of kits per litter 3 wk after whelping. Results were pooled for statistical analysis. Bovine INH antibody titers (percent 125I-bINH bound to serum diluted 1:8000) were 53 ± 3% vs. 2 ± 0.6%, and serum concentrations of FSH were higher (p < 0.05) in bINH-immunized mink compared with controls (144 ± 23 vs. 67 ± 12 ng/ml). However, number (3.8 ± 0.2 vs. 5 ± 0.4) and weight (8 ± 0.3 vs. 9.7 ± 0.4 g) of kits per litter at birth and number of kits per litter alive 3 wk after birth (2.9 ± 0.5 vs. 4.7 ± 0.4) were lower (p < 0.05) in bINH-immunized mothers compared with controls. During the nonbreeding season in 1991, a single injection of hCG (100 IU) was administered to bINH-immunized and control mink; 24 h later blood was sampled, and organ weights were determined. Titers of bINH antibodies (40 ± 4.4 vs. 2 ± 0%), concentrations of FSH (116 ± 22 vs. 48 ± 15 ng/ml), and uterine weights (407 ± 27 vs. 323 ± 26 mg) were greater (p > 0.05) in bINH-immunized mink compared with controls. We conclude that inhibin has a key role in regulation of FSH secretion and may have a physiological role important for embryo development and survival in mink.