Effects Of Exogenous T3 On The Growth Trait And Liver Deiodinases Expression During Late-term Embryonic And Early Post-hatch Development In Jinding Ducks

Duck meat production depends on The occurrence of skeletal muscles during embryonic period. Two breeds of ducks had different growth rate were compared and we found that albumen’s T3 concentration in ducks growed more quickly were significant higher than that in ducks growed slowly. Therefore, we assumed that T3 concentration in albumen was positively related to ducks’ growth speed and ducks’ growth can be promoted when the T3 concentration was increased in albumen. In ovo T3 administration was employed then to verify the hypothesis and ducks’ growth, serum thyroid hormones(THs), deiodinases expression in liver controlling THs level stabilization, were determined during late-term embryonic and early post-hatch periods. The mode of exogenous T3 interfering duck embryo hepatocyte growth in vitro was conducted aimed at investigating the deiodinases’ expression in liver cells. The effect of exogenous T3 on ducks’ growth and liver deiodinases expression during late-term embryonic and early post-hatch periods were investigated in the present study. 1 Effects of in ovo T3 administration on ducks’ growth and Serum THs concentration during late-term embryonic and early post-hatchTwo hundred of Jinding duck eggs were divided into two groups randomly, namely control group and treated group. Then 100 μL physiological saline solution without T3 were injected into control group eggs’ albumen from the sharp end of eggs. 250 ng of T3 were injected into the treated group’s eggs from the same place and 100 μL physiological saline solution was used as the carrier, before the incubation. All the eggs were incubated at the same condition. Body weights and pectorales weights were recorded, serum and pectorales were collected at the embryonic day 27 and 7 day of post hatch. Serum concentration of T3 and T4 were measured with radioimmunoassay method. The correlation between Body weights, pectorales weights and T3 and T4 concentration were analyzed. The results showed that body weight and pectorales weights were significant improved during late-term embryonic and early post-hatch periods(P = 0.035, 0.044; 0.027, 0.037). The concentration of T3 and T4 were significant declined at 7 day post-hatch(P = 0.040, 0.040). There was a significantly negative correlation between serum T3 concentration and ducks’ body weight during late-term embryonic and early post-hatch periods(r =-0.821, P = 0.000). 2 Effects of in ovo T3 administration on liver deiodinases expression during late-term embryonic and early post-hatchExperimental design was the same as above, and ducks’ liver were collected at the embryonic day 27 and the age of 7 day.(deiodinase I, D1) and(deiodinase Ⅲ, D3) m RNA expression were measured using Real-time PCR(RT-PCR) method in liver. The protein concentration was measured and activities of D1 and D3 in liver were detected with enzyme-linkedimmunosorbentassay(ELISA)method. The results showed that protein concentration and enzyme activities of D1 and D3 as well as D3 m RNA expression were significant down-regulated the age of 7 day post hatch(P = 0.017, 0.042; 0.013, 0.039; 0.049). There was a significantly positive linear correlation between serum T4 concentration and D3 m RNA expression(r = 0.913, P = 0.001). There were also a significant positive linear correlation between serum T3 and D1, D3 protein concentration as well as enzyme activities during late-term embryonic and early post-hatch.(r = 0.790, P = 0.011; r = 0.746, P = 0.021; r = 0.757, P = 0.018; r = 0.744, P = 0.022). 3 Effects of exogenous T3 on the deiodinases m RNA expression and activity in hepatic cellsDucks’ liver cells at the embryonic day 15 were collected and cultured for 24 h, and they were devided into three groups, namely Control group(Con), Low T3 interference group(LT3) and High T3 interference group(HT3). Then 2 μL physiological saline solution without T3 was added into the Con and final concentration 5 ng/m L and 20 ng/m L T3 were added into the LT3 and HT3, respectively. and physiological saline solution was used as the carrier. All the medium were replaced after the cells were cultured for 36 h, then the cells were cultured for 12 h continuely. The cells’ living activities were evaluated by Cell Counting Kit-8(CCK-8), and D1 and D3 m RNA expression were determined with Real-time fluorescent quantitative PCR(RT-QPCR) at 0 h and 12 h after T3 interference. Meanwhile, the protein concentration and activities of D1 and D3 in liver were detected with enzyme-linkedimmunosorbentassay(ELISA) analysis. The results showed that the LT3 cells activity were significant higher than that in control groups at 0 h and 12 h(P = 0.026, 0.006). LT3 D1 m RNA expression were significantly up-regulated at 0 h and 12 h(P = 0.000, 0.000).In conclusion, There was some correlation between the difference of T3 concentration in albumen and ducks’ early growth, 250 ng exogenous T3 promoted the gain of ducks’ body weight and pectorals weight during late-term embryonic and early post-hatch periods, and reduced serum T3 and T4 concentrations after incubation; Ducks’ growth pattern were changed, accompanied with the reduction of liver D3 m RNA expression during late-term embryonic as well as the reduction of D1 and D3 protein concentrations, enzyme activities at early post-hatch period; The direct regulation function of D1 to T3 was verified by the exogenous T3 interfered ducks embryo primary hepatocyte growth.