卵巢摘除对山羊血清GH水平和组织中GHR基因表达的影响

Effects of Ovariectomy on Serum GH Levels and Expression of GHR in Some Tissues of Female Goats

【目的】探讨卵巢摘除对母山羊产肉性能,血清中生长激素(growth hormone,GH)水平以及背最长肌、股二头肌、肝脏、脂肪组织中生长激素受体基因(growth hormone receptor,GHR)表达的影响,揭示摘除母山羊卵巢提高其育肥效果的原因。【方法】将体重相近的5月龄布尔山羊杂种(布尔山羊♂×关中奶山羊♀)母羊40只作为研究对象。试验开始前一个月,对所有羊只进行驱虫和防疫工作。试验开始时将母羊随机分为处理组和对照组,每组20只,摘除处理组母羊的卵巢,对照组不摘除。在试验的第0,10,20,30,40和50天早晨8:00对所有试验羊进行空腹采血,立即分离血清,采用羊生长激素酶联免疫分析试剂盒测定血清中GH水平。50d后分别从处理组和对照组随机选取5只试验羊进行屠宰试验,测定其屠宰率、胴体产肉率、眼肌面积和骨肉比。同时,立即采取肝脏、背最长肌、股二头肌及肾周脂肪组织样,每个组织至少采集3份生物学重复样,用锡箔纸包好标记后立即投入液氮中,带回实验室放入-80℃冰箱保存,然后利用实时荧光定量PCR(qRT-PCR)相对定量技术和2-△△Ct法检测背最长肌、股二头肌、肝脏和肾周脂肪中GHR基因mRNA的相对表达量。【结果】对照组母羊血清GH浓度在试验的第20天为8.63μg·L-1,处理组母羊达到9.50μg·L-1,显著高于对照组(P<0.05),且随着试验进行呈上升趋势。处理组母羊血清GH浓度在第50天时达到了11.55μg·L-1,高出对照组(9.34μg·L-1)2.21μg·L-1,且两组间差异极显著(P<0.01)。另外,发现处理组母羊的屠宰率、胴体产肉率和眼肌面积均高于对照组,且处理组母羊屠宰率达到了45.62%显著高于对照组的42.41%(P<0.05),但是骨肉比则显著低于对照组(P<0.05)。实时荧光定量PCR的结果显示处理组母羊肝脏中GHR基因mRNA的表达量是对照组的3.21倍(P<0.01);GHR基因在处理组母羊背最长肌中的相对表达水平最高,是对照组的4.87倍,且两组间差异极显著(P<0.01);股二头肌中GHR基因表达量是对照组的3.17倍,差异极显著(P<0.01);在肾周脂肪中,处理组母羊GHR基因的相对表达量是对照组的1.91倍,显著高于对照组(P<0.05)。【结论】摘除母山羊卵巢后,其屠宰率、血清GH水平以及肝脏、背最长肌、股二头肌和肾周脂肪GHR基因表达均显著上升,骨肉比显著下降。这提示摘除母畜卵巢可能通过增加其血清GH水平和部分靶组织中GHR基因的表达提高母羊的屠宰率,降低骨肉比,从而有利于母羊的产肉性能的提高。

[Objective]This study was conducted to investigate the effects of ovariectomy on the meat performance, serum GH （growth hormone） levels and the relative expression levels of GHR （growth hormone receptor） mRNA in longissimus and biceps femoris tissues, liver and perirenal fat tissue, and to reveal the reasons of fattening after ovariectomy in female goats.[Method]Forty young hybrid does Kid of Boer Goats （Boer goat♂＆#215; Guanzhong dairy goat♀） with similar body weight at about 5 months old were randomly divided into treatment group （n=20） and control group （n=20）, the works of insect repellent and epidemic prevention were implemented a month ago before the beginning of the experiment. The goats in the treatment group were ovariectomized at the beginning of the experinment and the goats were not done in control group. Venous blood samples （10 ml） were collected from each goat to separate serum via jugular vein puncture using clean sterile syringes and needles with no additive at 8：00 in the morning on days 0, 10, 20, 30, 40 and 50 during the experiment. Then the serum was separated from blood samples to determine the levels of the growth hormone （GH） with specific ELISA kits （enzyme-linked immunosorbent assay kit） according to the manufacturer’s instruction. The slaughter rate, lean percentage of carcass, loin eye area and proportion of bone and meat were measured after 10 goats （5 goats of each group） were slaughtered on the 50 th day. At the same time, longissimus and biceps femoris tissues, liver and perirenal fat samples were collected immediately after goats were sacrificed, then three biological replicates were collected at each sample, and the samples were rinsed with sterile saline to remove blood clots and wrapped in aluminum foil with good marks, shock-frozen in liquid nitrogen. The mRNA expression levels of GHR gene in liver, longissimus muscle, biceps femoris and perirenal fat were detected with real-time quantitative PCR （qRT-PCR） and the method of 2-ΔΔCt （the Ct mean value of threshold cycle）.[Result]The serum GH levels of the ovariectomized goats on the 20th day showed an upward trend and were up to 9.50μg＆#183;L-1 which were significantly higher than those of the controls （P＆lt;0.05）. On the 50th day, the levels were up to 11.55 μg＆#183;L-1 that was 2.21μg＆#183;L-1 higher than those of the control group （9.34μg＆#183;L-1） significantly （P＆lt;0.01）. In addition, the goats in treatment group with higher slaughter rate, lean percentage of carcass and loin eye area compared with that in the control group. The slaughter rate in ovariectomized goat was up to 45.62%which was higher than that in the control group （42.41%） and the difference was significant （P＆lt;0.05）, but the goats had a lower proportion of bone and meat （P＆lt;0.05） in treatment group. In this study, the expression levels of GHR gene in liver of ovariectomized goats were 3.21 times （P＆lt;0.01） more than that of the control group. Compared with the control group, a very significant increase in the GHR mRNA level was observed in longissimus of ovariectomized goats, and the expression level was the highest in the present study which was 4.87 times higher than that of the control group （P＆lt;0.01）. At the same time, a higher expression of GHR mRNA in biceps femoris （3.17 times） was also observed in ovariectomized goats, and the difference was significant compared with the control group （P＆lt;0.05）. As to perirenal fat, the expression levels of GHR gene in treatment group was 1.91 times more than that in the control group, and the difference was significant （P＆lt;0.05）[Conclusion] Results of the study showed that there were significant effects of ovariectomy on slaughter rate, proportion of bone and meat, serum GH levels. Meanwhile, the expression levels of GHR gene in liver, longissimus muscle, biceps femoris and perirenal fat tissues of female goats were also influenced by the ovariectomy. It is indicated that the ovariectomy increased the slaughter rate and decreased the proportion of bone and meat through enhancing the levels of serum GH and expression levels of GHR gene in the target tissues, and improved the meat performance of ovariectomized goats finally.