Effects of short photoperiod on the expression of Smad2 and Smad3 mRNA in Syrian hamster testis

The testicular localization and expression of Smad2 and Smad3 mRNA involved in the intracellular signal transduction of activin, inhibin and transform ing growth factor-beta (TGF-beta) were examined under the influence of long and short photoperiod in Syrian hamsters (Mesocricetus auratus). In situ h ybridization detected both Smad2 and Smad3 mRNA in spermatogonia and premei otic spermatocytes in the active testis exposed to a long photoperiod, as w ell as in the regressed testis exposed to a short photoperiod. Northern blo ts showed that Smad2 mRNA was expressed at all stages over long and short p hotoperiods, whereas Smad3 mRNA was expressed at high levels in the photope riod-induced regressed testis. The photoperiodic condition would change the balance between Smad2 and SmadS transcripts in the testis. Thus, intracell ular Smad2 and Smad3 might participate in transducing signals from activin, inhibin and TGF-beta in spermatogenetic cells.