The Syrian hamster is a seasonal breeder that undergoes a testicular regression when exposed to a short day photoperiod (SD, 6 h light per day) for 16 weeks, and a subsequent gonadal reactivation after longer times of permanence in SD. In this study, we investigated the role of melatonin (Mel) and prolactin (PRL), key players in the recrudescence phase, on testicular cyclooxygenase 2 (COX2) expression and prostaglandins (PGs) production during the photoperiodic regressionreactivation transition. The number of COX2-immunoreactive Leydig cells/mm2 (COX2 LC) and the plasma levels of PRL were determined by immunohistochemistry and RIA, respectively, in hamsters maintained in a long day photoperiod (LD, 14 h light per day) or exposed to SD for 9, 12, 16, 22 and 28 weeks.
Furthermore, PRL significantly induced COX2 protein expression and PGF2α production in purified Leydig cells from LD and 16SD hamsters, while Mel inhibited COX2 mRNA expression. In conclusion, our results reflect the participation of PRL and Mel as modulators of COX2 expression and PGs production during the photoperiodic-induced testicular active-inactive transition in hamsters.
Prague, Czech Republic
24 - 28 Apr 2010
European Society of Endocrinology