Endocrine Abstracts (2010) 22 P522

Effect of prolactin (PRL) and melatonin (Mel) in the regulation of cyclooxygenase 2 (COX2) expression in Syrian hamster Leydig cells

Maria Matzkin1,2, Soledad Rossi1, Ricardo Calandra1 & Monica Frungieri1,2

1Institute of Biology and Experimental Medicine, CONICET, CABA, Buenos Aires, Argentina; 2School of Medicine, CABA, Buenos Aires, Argentina.

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 regression–reactivation 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.

COX2 LC176.8±11.1143.8±28.995.0±10.714.7±7.4103.5±12.8107.7±22.2
PRL (ng/ml)17.2±2.74.6±1.80.7±0.10.4±0.032.4±0.96.8±1.1

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.

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