不同光照周期对雌兔卵泡发育和下丘脑-垂体-卵巢轴的影响

doi:10.11843/j.issn.0366-6964.2019.08.019

摘要/Abstract

摘要： 本研究旨在观察不同光照周期对母兔的发情率、同期发情和性腺轴的影响并探讨其机制。选用5月龄未经产新西兰母兔48只，随机分成3组，每组16只，前10 d各试验组采用“12 h光照∶12 h黑暗”的光照制度，后6 d分别采用长光照（16 h光照∶8 h黑暗）、短光照（8 h光照∶16 h黑暗）和正常光照（12 h光照∶12 h黑暗，对照组）的光照制度，光照强度80 lx。试验结束后统计发情率，并采集血清、下丘脑、垂体和卵巢，用ELISA、HE染色、RT-PCR的方法，研究不同光照周期下对雌兔卵泡发育和激素的影响。结果表明：长光照组血清褪黑激素水平比对照组显著低34.8%（P<0.05）、比短光照组显著低47.8%（P<0.05），而短光照组比对照组高25%（P<0.05）。长光照组母兔下丘脑分泌GnRH mRNA表达显著增强，其mRNA表达量比短光照组显著升高453%（P<0.05），比对照组显著升高250%（P<0.05）；而短光照组的比对照组降低36.7%（P>0.05）。同样，长光照组母兔垂体的GnRH mRNA表达量较短光照组、对照组分别高70%和41.7%，差异显著（P<0.05）；短光照组则比对照组降低16.7%（P>0.05）。长光照组的血清卵泡刺激素水平分别比短光照组、对照组高33.7%和25.1%，差异显著（P<0.05）。长光照组血清促黄体生成素含量比短光照组显著高54.2%（P<0.05）。长光照组血清雌二醇水平较对照组显著高34.8%（P<0.05），较短光照组显著高47.8%（P<0.05）；短光照组比对照组低17.6%（P>0.05）。长光照组的单位面积初级卵泡数显著多于短光照组120%（P<0.05）和对照组68.3%（P<0.05），短光照组与对照组相比差异不显著（P>0.05）。3个试验组卵巢单位面积窦状卵泡数没有显著差异（P>0.05）。长光照组的发情率为81.25%，而短光照组的仅为12.5%，对照组的发情率为31.25%。由本试验可知，长光周期组可抑制褪黑激素分泌、促进下丘脑分泌GnRH活性增强、提高垂体细胞GnRH受体表达、促进垂体分泌LH、FSH、提高了血清中LH、FSH的水平、促使雌二醇分泌、卵泡发育、成熟和排卵，诱导母兔同期发情。

关键词: 光照周期, 兔, 同期发情, 激素, GnRH

Abstract: In this study, we investigated the effects and mechanisms of estrus rate, estrus and gonadal axis on female rabbits. A total of 48 5-month-old female New Zealand rabbits, not multiparous, were reared in artificial illumination. They were randomly assigned to 3 groups of 16 each. All groups were reared in 12-h L/12-h D photoperiod for the first 10 days, then the 3 groups were reared in long light group (LD, L:D 16:8), control group (L:D 12:12) or short light group (SD, L:D 8:16) for the last 6 days separately. Light intensity is 80 lx. The blood, hypethalamus, pituitary and ovary were collected, and estrus ratio was recorded. Effects of photoperiod on secretion of development of follicular and gonadotropic hormone were investigated by HE staining, ELISA, real-time PCR methods. Our results revealed that the serum melatonin level in LD was significantly decreased by 34.8%, 47.8% compared to control and SD groups (P<0.05). Meanwhile,the serum melatonin level in SD was 25% higher than that of control group (P<0.05). The GnRH mRNA expression of the hypothalamus in the rabbit exposed to LD was increased. The GnRH mRNA level of hypothalamic significantly increased by 453%, 250% compared to SD and control groups (P<0.05), while there was no significant difference between SD group and control group (P>0.05). Similarly, the GnRH mRNA level of the pituitary exposed to LD significantly was increased by 70%, 41.7% compared to SD group and control group (P<0.05), while there was no significant difference between SD group and control group (P>0.05). The level of serum follicle stimulating hormone(FSH) in the LD group was 33.7% and 25.1% higher than those of SD group and control group significantly (P<0.05, respectively). Serum luteinizing hormone(LH) level in the LD group was significantly increased by 54.2% as compared to SD group (P<0.05). The level of serum estradiol in the LD group was significantly increased by 34.8%, 47.8% compared to control group and SD group (P<0.05). The number of primary follicles per unit area in long photoperiod group was 120% and 68.3% higher than those of short photoperiod group and the control group (P<0.05). There were no significant differences in the number of antral follicles per unit area of the ovary among groups (P>0.05). Compared to control group (31.25%), estrus ratio of long photoperiod group increased to 81.25%, while that of short photoperiod group reduced to 12.5%. Melatonin plays a critical role in the mechanism by which photoperiod affects estrus of female rabbit. Long photoperiod reduces the secretion of melatonin, which promotes the secretion of GnRH in hypothalamus and the expression of GnRH in pituitary. Furthermore, the serum LH, FSH level were elevated, which increasing estradiol secretion, and promoting the development mature of follicles. Finally, it induces the estrus of the female rabbit.

Key words: photoperiod, rabbit, synchronization of estrus, hormone, GnRH

中图分类号:

S852.16

张玉仙, 王文利, 原展航, 白欣洁, 王子旭, 曹静, 董玉兰, 陈耀星. 不同光照周期对雌兔卵泡发育和下丘脑-垂体-卵巢轴的影响[J]. 畜牧兽医学报, 2019, 50(8): 1694-1701.

ZHANG Yuxian, WANG Wenli, YUAN Zhanhang, BAI Xinjie, WANG Zixu, CAO Jing, DONG Yulan, CHEN Yaoxing. The Effect of Different Photoperiods on Follicular Development and Hypothalamus-Pituitary-Ovary Axis in Female Rabbits[J]. ACTA VETERINARIA ET ZOOTECHNICA SINICA, 2019, 50(8): 1694-1701.

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