Fail P A, Whitsett J M
Interdepartmental Physiology Program, North Carolina State University, Raleigh.
J Androl. 1988 Jan-Feb;9(1):21-30. doi: 10.1002/j.1939-4640.1988.tb01004.x.
Four experiments were designed to investigate the influence of photoperiod and other environmental factors on androgen production and reproductive maturation in deer mice. Male prairie deer mice (Peromyscus maniculatus), born in a light/dark cycle of 6L:18D, either remained in this short photoperiod or were switched to a long day regimen of 16L:8D at weaning. In a cross-sectional experiment, the deer mice were killed between 3 and 8 weeks of age for measurement of serum testosterone concentration and reproductive organ weights. In a second experiment, blood was collected from each mouse at weekly intervals between 3 and 9 weeks of age. This repeated measures design was used to reduce the high variability in testosterone values observed in the first experiment. Reproductive organs were weighed at the termination of the experiment. Testosterone concentrations and reproductive organ weights were greater in males reared in the long photoperiod in both experiments. In a third experiment, the animals were housed under five different conditions to test the influence of high ambient temperature and melatonin as well as photoperiod. At 7 weeks of age, they received an injection of hCG or saline. More testosterone was released in deer mice reared in 16L:8D and 27 C than in those reared in short days (6L:18D) or those reared in high ambient temperature (35 C) or those treated with exogenous melatonin. One week later, animals were sacrificed. The single hCG treatment caused significant reversal of the suppression of accessory sex organ weights following melatonin, short days or 35 C temperature. In a fourth experiment, the additive influence of melatonin and 35 C temperature was tested. Animals treated with 35 C or both melatonin and 35 C had lower serum testosterone at 7 weeks of age, released less testosterone after hCG, and had smaller organ weights with or without hCG than long day controls. The influence of melatonin treatment and 35 C temperature appears to be additive for testicular weight and testosterone release after hCG. Thus, the attenuation of reproductive development that accompanied short days, melatonin treatment and high ambient temperature occurred via diminished testosterone secretion, which can be overcome at least in part by gonadotropin treatment.
设计了四项实验来研究光周期和其他环境因素对鹿鼠雄激素产生和生殖成熟的影响。雄性草原鹿鼠（白足鼠）出生于6小时光照：18小时黑暗的光/暗周期，要么一直处于这种短光周期，要么在断奶时转换为16小时光照：8小时黑暗的长日照方案。在一项横断面实验中，鹿鼠在3至8周龄时被处死，以测量血清睾酮浓度和生殖器官重量。在第二项实验中，在3至9周龄期间每周从每只小鼠采集血液。这种重复测量设计用于减少在第一项实验中观察到的睾酮值的高变异性。在实验结束时称量生殖器官重量。在两项实验中，在长光周期饲养的雄性鹿鼠中，睾酮浓度和生殖器官重量都更高。在第三项实验中，将动物饲养在五种不同条件下，以测试高环境温度、褪黑素以及光周期的影响。在7周龄时，它们接受人绒毛膜促性腺激素（hCG）或生理盐水注射。与在短日照（6小时光照：18小时黑暗）、高环境温度（35摄氏度）或接受外源性褪黑素处理的鹿鼠相比，在16小时光照：8小时黑暗和27摄氏度条件下饲养的鹿鼠释放的睾酮更多。一周后，处死动物。单次hCG处理导致在褪黑素、短日照或35摄氏度温度处理后附属生殖器官重量抑制的显著逆转。在第四项实验中，测试了褪黑素和35摄氏度温度的叠加影响。在7周龄时，接受35摄氏度或同时接受褪黑素和35摄氏度处理的动物血清睾酮较低，在hCG处理后释放的睾酮较少，并且无论有无hCG，其器官重量都比长日照对照组小。褪黑素处理和35摄氏度温度的影响对于hCG处理后的睾丸重量和睾酮释放似乎是叠加的。因此，短日照、褪黑素处理和高环境温度伴随的生殖发育减弱是通过睾酮分泌减少发生的，这至少可以部分通过促性腺激素处理来克服。
