雄性大熊猫褪黑素与睾酮季节性变化

Seasonal Changes in Melatonin and Testosterone Levels in Male Giant Pandas

褪黑素通过调控下丘脑-垂体-性腺内分泌轴使季节性繁殖动物在适宜的季节进行繁殖活动。大熊猫(Ailuropoda melanoleuca)在春季集中繁殖。为探究雄性大熊猫褪黑素和睾酮的季节性变化规律,本研究选取成都大熊猫繁育研究基地3只成年雄性大熊猫作为实验对象,在自然光照下对这3只大熊猫进行每周1次为期1年(2018年8月至2019年7月)的尿液样品采集。依据当地气候情况,将3至5月作为春季,6和7月为夏季,8至11月为秋季,12月至翌年2月为冬季。采用酶联免疫法(ELISA)测定尿样中褪黑素和睾酮水平。采用单因素方差分析(one way-ANOVA)及独立样本T检验对四个季节激素水平进行差异性分析。结果表明,褪黑素水平在冬季分别极显著高于秋季、春季及夏季(P<0.01),秋季、春季以及夏季三个季节间差异不显著(P>0.05)。睾酮水平在冬季分别极显著高于秋季与夏季(P<0.01),春季亦分别极显著高于秋季与夏季(P<0.01),但冬季与春季差异不显著(P>0.05),秋季与夏季亦差异不显著(P>0.05)。研究表明,雄性大熊猫褪黑素和睾酮分泌水平呈现出季节性变化,从秋季到冬季,雄性大熊猫褪黑素和睾酮水平同步升高,从冬季到春季繁殖季节,褪黑素水平极显著下降,但睾酮仍处在高位水平。该研究结果可为进一.步研究褪黑素对大熊猫季节性繁殖影响提供基础数据。

Melatonin is important for seasonal breeding animals to display their breeding characteristics in an appropriate season by regulating the hypothalamic-pituitary-gonadal axis.The Giant Panda(Ailuropoda melanoleuca)is a seasonal breeding mammal,usually breeding from March to May.[Objectives]To explore the seasonal changes in melatonin and testosterone in male giant pandas,[Methods]urine samples from three adult male giant pandas housed at the Chengdu Research Base of Giant Panda Breeding were collected once a week for one year(2018.8-2019.7)under natural photoperiod conditions.Depending on the local climate,spring is from March to May,summer includes June and July,autumn is from August to November,and winter is from December to February of the following year.These samples were analyzed for urinary melatonin and testosterone levels by ELISA.The seasonal changes of melatonin and testosterone levels were analyzed by one one-way ANOVA,and the differences of inter-seasonal data were analyzed by independent sample t-test.The data of testosterone levels were adjusted for homogeneity of variance by using the log value for analysis,however,all graphs were expressed in the actual testosterone levels.[Results]The results indicated that melatonin levels showed a seasonal secretion pattern(Fig.1 and 2)and its level in winter was extremely significantly higher than that in in autumn,spring and summer,respectively(P<0.01),and there were no significant differences among the levels in autumn,spring or summer(P>0.05).Testosterone levels also showed a seasonal secretion pattern(Fig.3 and 4)and its level in winter was extremely significantly higher than that in autumn or summer(P<0.01).Testosterone level in spring was also extremely significantly higher than that in autumn or summer(P<0.01),however no significant difference was detected between winter and spring(P>0.05).Additionally,there was no significant difference between autumn and summer either(P>0.05).[Conclusion]Urinary melatonin and testosterone levels show seasonal changes.Melatonin and testosterone levels increase synchronously from autumn to winter;melatonin level decreases sharply,while testosterone remains at a high level from winter to spring.The results provide reference data for further investigation of the effect of melatonin on the seasonal breeding of giant pandas.