Comparative analysis of activins A and B in the adult mouse epididymis and vas deferens.

Activin A regulates testicular and epididymal development, but the role of activin B in the epididymis and vas deferens is unknown. Mouse models with reduced activin A ( and ), or its complete absence (), were investigated to identify specific roles of activins in the male reproductive tract. In 8-week-old mice, serum activin A decreased by 70%, with a 50% reduction of gene expression and protein in the testis, epididymis and vas deferens. Activin B and the activin-binding protein, follistatin, were similar to wild-type. Testis weights were slightly reduced in mice, but the epididymis and vas deferens were normal, while the mice were fertile. Activin A was decreased by 70% in the serum, testis, epididymis and vas deferens of mice and was undetectable in mice, but activin B and follistatin levels were similar to wild-type. In 6-week-old mice, testis weights were 60% lower and epididymal weights were 50% lower than in either or wild-type mice. The cauda epididymal epithelium showed infoldings and less intra-luminal sperm, similar to 3.5-week-old wild-type mice, but at 8 weeks, no structural differences in the testis or epididymis were noted between and wild-type mice. Thus, can compensate for in regulating epididymal morphology, although testis and epididymal maturation is delayed in mice lacking Crucially, reduction or absence of activin A, at least in the presence of normal activin B levels, does not lead to major defects in the adult epididymis or vas deferens.