Effects of photoperiod on testicular inhibin-alpha and androgen binding protein mRNA expression during postnatal development in Siberian hamsters, Phodopus sungorus.

The effects of short photoperiod (SPP) on testicular inhibin-alpha and androgen binding protein (ABP) mRNA expression were investigated in Siberian hamsters during postnatal development. Hamsters were raised in either long photoperiod (LPP; 16L:8D) or in a SPP (6L:18D). Hamsters were sacrificed at the following developmental ages: preweaning (18-20 days), immature (28-30 days), pubertal (38-40 days), postpubertal (48-50 days) and adult (60-62 days; n = 7-12 animals per group). Body and testicular weights were determined and plasma FSH levels were measured by validated RIA. As expected, testicular weight and circulating FSH levels were significantly lower in hamsters raised in SPP than in LPP animals. Photoperiod had no significant effect on body weight except during postpubertal age. The northern analyses of inhibin-alpha and ABP expression in the testes revealed that the corresponding relative mRNA levels were higher in animals exposed to SPP than in animals from LPP. These findings suggest that the testes of hamsters exposed to a SPP can synthesize inhibin-alpha and ABP, and we speculate that the release of these proteins may be regulated by photoperiod and the role of FSH in the control of inhibin-alpha and ABP gene expression in male Siberian hamsters may be minimal.