Changes in the Immunolocalization of Steroidogenic Enzymes and the Androgen Receptor in Raccoon (Procyon lotor) Testes in Association with the Seasons and Spermatogenesis

The raccoon is a seasonal breeder with a mating season in the winter. In a previousstudy, adult male raccoons exhibited active spermatogenesis with high plasma testosteroneconcentrations, in the winter mating season. Maintenance of spermatogenesis generallyrequires high testosterone, which is produced by steroidogenic enzymes. However, even inthe summer non-mating season, some males produce spermatozoa actively despite low plasmatestosterone concentrations. To identify the factors that regulate testosterone productionand contribute to differences in spermatogenetic activity in the summer non-mating season,morphological, histological and endocrinological changes in the testes of wild maleraccoons should be known. In this study, to assess changes in the biosynthesis, metabolismand reactivity of testosterone, the localization and immunohistochemical stainingintensity of four steroidogenic enzymes (P450scc, P450c17, 3βHSD, P450arom) and theandrogen receptor (AR) were investigated using immunohistochemical methods. P450scc andP450c17 were detected in testicular tissue throughout the year. Seasonal changes intestosterone concentration were correlated with 3βHSD expression, suggesting that 3βHSDmay be important in regulating the seasonality of testosterone production in raccoontestes. Immunostaining of P450arom and AR was detected in testicular tissues thatexhibited active spermatogenesis in the summer, while staining was scarce inaspermatogenic testes. This suggests that spermatogenesis in the raccoon testis might bemaintained by some mechanism that regulates P450arom expression in synthesizing estradioland AR expression in controlling reactivity to testosterone.