Age-dependent pattern of connexin43 expression in testes of European bison (Bison bonasus, L.).

Morphology and the expression of connexin43 (Cx43) was investigated in testes of immature, prepubertal, and adult European bison bulls by means of routine histology, immunohistochemistry, and Western blotting, respectively. Testes were collected from culled animals living in Bialowieza and Borecka Forests, Poland. Histological examination of testicular tissue of immature and prepubertal males revealed normal structure, whereas of adult individuals either normal testicular structure with advanced spermatogenesis or varying degrees of tubule and interstitial tissue abnormality were seen. Immunohistochemical studies revealed Cx43 signal mostly at Leydig cell membrane appositions. In testes of immature males heterogeneous staining was observed; its intensity markedly increased in prepubertal males reaching almost two times more intense staining in adults. Strong Cx43 signal between Leydig cells was also observed in testes with structural alterations; however, sporadically it was of weak linear pattern. In the tubules of the latter, the intensity of Cx43 staining was weak to moderate or it was even absent. Immunohistochemical qualitative analysis was confirmed by quantitative image analysis in which the staining intensity was expressed as relative optical density of diaminobenzidine deposits. Data from Western blot analyses confirmed the results obtained by immunohistochemistry; immunodetectable Cx43 protein as a band of 43 kDa was detected in all testes samples. Overall, the increase in Cx43 level in testes along the bison postnatal development may be capable of a better exchange of metabolites and coordinating Leydig cell activity during maturation. A relationship between homozygosity occurring in European bison and altered intercellular communication is suggested.