蛋清内注射三碘甲腺原氨酸对鸭出雏前后生长发育、血清中甲状腺激素水平及肝脏中D1和D3表达的影响

Effects of in ovo T3 Administration on Development, Serum Thyroid Hormone Levels, Hepatic D1 and D3 Expression in Ducks During Late-Term Embryonic and Early Post-Hatch Development

【目的】以金定鸭为研究对象,孵化前向蛋清内注射三碘甲腺原氨酸(triiodothyronine,T3),检测鸭出雏前后体重、胸浅肌重、血清中甲状腺激素(thyroid hormones,THs)水平的变化,分析肝脏中I型脱碘酶(deiodinases I,D1)和Ⅲ型脱碘酶(deiodinasesⅢ,D3)m RNA表达、蛋白水平及酶活性的变化,探究外源性T3对鸭出雏前后生长发育及肝脏中脱碘酶表达的影响。【方法】将200枚金定鸭种蛋随机分为对照组和试验组,在孵化前从蛋的锐端往试验组种蛋蛋清内注射100μL含250 ng T3的生理盐水,对照组注射不含T3的100μL生理盐水,两组种蛋在相同条件下同期孵化。在27胚龄和7日龄时,记录鸭的体重和胸浅肌重,采用放射免疫分析法检测鸭血清中T3和四碘甲腺原氨酸(thyroxine,T4)水平,利用实时荧光定量PCR检测鸭肝脏中D1和D3的m RNA表达,利用酶联免疫吸附测定(enzyme-linked immunosorbent assay,ELISA)法检测鸭肝脏中D1和D3蛋白水平及酶活性。【结果】在27胚龄和7日龄时试验组鸭的体重(P=0.035,0.044)和胸浅肌重(P=0.027,0.037)均显著高于对照组;试验组血清中T3和T4水平在27胚龄时与对照组之间差异不显著(P>0.05),而7日龄时均显著低于对照组(P=0.040,0.040);试验组鸭肝脏中脱碘酶m RNA表达量仅D3在7日龄时显著低于对照组(P=0.040);在7日龄时试验组鸭肝脏中D1和D3的蛋白含量和酶活性亦均显著低于对照组(P=0.017,0.045;P=0.013,0.039)。鸭出雏前后的胸浅肌重与血清中T3水平呈强的负线性相关(r=-0.431,P=0.025);血清中T3水平与肝脏中D3的m RNA表达呈极显著正向相关(r=0.778,P=0.005),血清中T4水平与D1和D3的蛋白水平和酶活性均呈正线性相关(r=0.685,P=0.020;r=0.662,P=0.026;r=0.710,P=0.014;r=0.705,P=0.015)。【结论】蛋清内注射T3促进了鸭出雏前后生长发育,同时伴随着出雏后循环中THs水平的降低,肝脏中D1和D3的表达发生下调。

【Objective】 To investigate the effects of exogenous triiodothyronine（T3） on development and deiodinases expression during late-term embryonic and early post-hatch development in newly hatched Jinding ducks, we injected fertile eggs with T3 or vehicle before incubation, observed the changes of body weight and the weight of pectoralis major（PM） in prenatally T3-exposed ducks, and analyzed serum thyroid hormones level as well as the m RNA expression, the protein level, and the activity of deiodinases I（D1） deiodinases Ⅲ（D3） in liver. 【Method】Two hundreds fertile Jinding breeder eggs were randomly divided into two groups and injected with 0 ng（the control group） or 250 ng（the treatment group） of T3 in 100 μL of normal saline from the sharp of eggs before incubation. All the eggs were hatched at the same time and under the same conditions. Body weights and the weight of PM were recorded, meanwhile. Serum T3 and T4 levels were detected by Radioimmunoassay（RIA）, deiodinases m RNA expressions were evaluated by Real-time fluorescent quantitative PCR（RT-QPCR）, deiodinases protein content as well as the activity in liver were evaluated by Enzyme-Linked Immunosorbent Assay（ELISA） at the embryonic day 27 and the age of 7 days. 【Result】The results showed that body weights（P = 0.035, 0.044） and the weight of PM（P = 0.027, 0.037） in the treatment group were higher than that in the control group on the embryonic day 27 and the age of 7 days. There were no significant difference in serum T3 and T4 levels between the treatment group and the control group on the embryonic day 27（P〉0.05）, but they were all declined compared with the control group at the age of 7 days（P = 0.040, 0.040）. The protein content and the activity of D1（P = 0.017, 0.013） and D3（P = 0.045, 0.039） as well as D3 m RNA expression（P = 0.040） in liver were all down-regulated compared with the control group at the age of 7 days. There was a significantly negative linear correlation between serum T3 level and the weight of PM during late-term embryonic and early post-hatch development（r =-0.431, P = 0.025）, T3 level and D3 m RNA expression in liver was significantly positive correlated（r = 0.778, P = 0.005）, but there was also a significantly positive linear correlation between T4 level and D1 protein, D1 activity, D3 protein, and D3 activity（r = 0.685, P = 0.020; r = 0.662, P = 0.026; r = 0.710, P = 0.014; r = 0.705, P = 0.015）. 【Conclusion】These results suggested that in ovo T3 administration promoted the ducks＇ development during perinatal period, meanwhile, along with the decline of circulating THs level and the down-regulation of D1 and D3 expression in liver after incubation.