Testicular gene expression of steroidogenesis-related factors in prepubertal, postpubertal, and aging dogs

Developmental and aging changes in testicular factors related to steroidogenesis are unknown in dogs. Using reverse transcription quantitative real-time PCR, this study examined testicular mRNA levels of CYP11A1 (P450 cholesterol side-chain cleavage enzyme, P450scc), CYP17A1 (P450 17α-hydroxylase/C17-20 lyase, P450c17), HSD3B2 (3β-hydroxysteroid dehydrogenase, 3β-HSD), CYP19A (P450 aromatase, P450arom), STAR (steroidogenic acute regulatory protein, StAR), cyclooxygenase (COX) -1 and COX-2 in prepubertal (4-6 months of age), postpubertal (1 year of age), and aging (2-18 years of age) dogs. Testicular mRNA levels for P450scc, 3β-HSD, StAR, COX-1, and COX-2 did not change from prepubertal to postpubertal stages, whereas that for P450arom markedly and abruptly increased and that for P450c17 gradually decreased. In postpubertal and aging dogs, a negative correlation was found between aging and testicular P450arom mRNA levels. Based on the rapid testicular growth observed during puberty, these results suggested that total testis gene expression for steroidogenesis-related factors, in particular for P450arom, increases during puberty in dogs. In addition, the decline in P450arom gene expression during aging may affect the ability to synthesize steroids in canine testes.