Inhibin Pro-aC as the Marker of Testicular Function in the Stallion

Abstract

Inhibin pro-αC is a precursor form of inhibin α-subunit. A large amount of inhibin pro-αC is secreted from testes in male animals, and it is considered to have an important role in the physiology of male reproduction. The purpose of this study was to determine the relationship between inhibin pro-αC and reproductive ability in the mature stallion. Peripheral blood samples were collected from normal stallions and anabolic steroid (nandrolone decanoate) treated stallions. Plasma concentrations of inhibin pro-αC were measured by an enzyme linked immunosorbent assay system. Circulating concentrations of inhibin pro-αC in normal stallions showed clear seasonal changes and the highest concentrations were observed in the breeding season (from March to June). After treatment with anabolic steroid, peripheral inhibin pro-αC levels rapidly decreased and reached significantly lower levels compared to the pre-treatment value (p<0.05). The variations of circulating inhibin pro-αC showed a high positive correlation with other testicular hormones. These results clearly demonstrate that circulating concentrations of inhibin pro-αC reflect spermatogenic ability due to seasonal change or treatment with anabolic steroid in the stallion, and it may be a useful new marker for testicular functions.