Li Jing-hua, Zhang Rui, Wang Bei-lei, Na Ren, Li Yuan, Zhao Xiu-juan, Liang Dong-chun, Guo Gang
Department of Endocrinology, Armed Police Force Medical College Hospital, Tianjin 300162, China.
Zhonghua Yu Fang Yi Xue Za Zhi. 2010 Aug;44(8):726-30.
To explore the effects of thyroid hormone on the expression of homeobox gene Nkx2.1 mRNA in child rat by supplying their hypothyroidism pregnant mother with different dose of levothyroxine (L-thyroxine, L-T(4)) in different times.
120 female Wistar rats were randomly divided into eight groups according to the body weight: control group, non-treatment hypothyroidism group, hypothyroidism groups supplied with L-T(4) in high, medium and low dosage in early stage (1st-17th day of pregnancy) and in late stage (18th day of pregnancy-20th day after childbirth). According to 100 grams of body weight, the concentrations of L-T(4) were 3.5, 2.0, 0.5 µg/d in high, medium and low dosage group. All the rats were fed with low-iodine food. The control group was given 200 µg/L potassium iodate solution as drinking water and the other groups were given deionized water. After three months, the rats were mated with normal male rats. After the pregnancy was confirmed, hypothyroidism groups were supplied with L-T(4) of different concentrations. Brain samples were taken from the 17-day fetal rats, new-born and 20-day old offsprings and the levels of Nkx2.1 mRNA in brain tissue were analyzed by real-time fluorescence quantitative PCR techniques.
The levels of TT(3) in hypothyroidism groups supplied with L-T(4) in high, medium and low dosages in early and late pregnant stages, non-treatment hypothyroidism group and control group were (0.85 ± 0.17), (0.81 ± 0.18), (0.86 ± 0.21), (0.85 ± 0.20), (0.89 ± 0.18), (0.85 ± 0.20), (0.86 ± 0.20), (1.08 ± 0.07) nmol/L (F = 4.08, P < 0.01); the levels of TT(4) in each group were (0.43 ± 0.16), (0.39 ± 0.11), (0.39 ± 0.13), (0.43 ± 0.17), (0.51 ± 0.19), (0.43 ± 0.16), (0.41 ± 0.15), (39.43 ± 14.16) nmol/L (F = 31.99, P < 0.01); the levels of FT(3) in each group were (3.29 ± 0.61), (3.29 ± 0.61), (3.24 ± 0.61), (3.28 ± 0.63), (3.31 ± 0.59), (3.28 ± 0.50), (3.24 ± 0.49), (4.93 ± 0.46) pmol/L (F = 5.79, P < 0.01); the levels of FT(4) in each group were (3.38 ± 0.80), (3.31 ± 0.67), (3.29 ± 0.73), (3.27 ± 0.71), (3.48 ± 0.81), (3.56 ± 0.66), (3.29 ± 0.61), (27.29 ± 4.53) pmol/L (F = 26.34, P < 0.01). The expression of Nkx2.1 mRNA in non-treatment hypothyroidism group (9.15 × 10(-5) ± 9.17 × 10(-5)) was lower than control group (65.1 × 10(-5) ± 40.90 × 10(-5)) in 17th day of pregnancy (t = 66.224, P < 0.05); the expression of Nkx2.1 mRNA in non-treatment hypothyroidism group (3.16 × 10(-5) ± 0.142 × 10(-5)) was lower than control group (55.6 × 10(-5) ± 51.05 × 10(-5)) in new-born (t = 102.225, P < 0.05); the expression of Nkx2.1 mRNA in non-treatment hypothyroidism group (8.09 × 10(-5) ± 8.21 × 10(-5)) was lower than control group (13.9 × 10(-5) ± 7.43 × 10(-5)) in 20th day after birth (t = 9.235, P < 0.05). The trend of Nkx2.1 mRNA in hypothyroidism groups was decreased in group supplied with L-T(4) in medium dosage in early stage descends in 17th day of pregnancy, new-born and 20th day after birth (57.1 × 10(-5) ± 22.90 × 10(-5)), (30.8 × 10(-5) ± 27.20 × 10(-5)), (17.1 × 10(-5) ± 0.623 × 10(-5)) (F = 13.394, P < 0.01). The expression of Nkx2.1 mRNA in hypothyroidism groups supplied with L-T(4) in medium dosage in early stage in 17th day of pregnancy, new-born and 20th day after childbirth was closest to the control group in every period (t values were 0.225, 0.336, 0.345, all P values > 0.05).
The difference in the expression of homeobox gene Nkx2.1 mRNA is highly related to the level of thyroid hormone.
通过在不同时期给患甲状腺功能减退症的孕鼠补充不同剂量的左甲状腺素（L-甲状腺素，L-T4），探讨甲状腺激素对幼鼠同源框基因Nkx2.1 mRNA表达的影响。
将120只雌性Wistar大鼠按体重随机分为8组：对照组、未治疗的甲状腺功能减退症组、孕早期（妊娠第1~17天）和孕晚期（妊娠第18天至产后第20天）给予高、中、低剂量L-T4的甲状腺功能减退症组。高、中、低剂量组L-T4按每100克体重分别为3.5、2.0、0.5μg/d。所有大鼠均喂低碘食物。对照组给予200μg/L碘酸钾溶液作为饮用水，其他组给予去离子水。3个月后，将大鼠与正常雄鼠交配。确认妊娠后，甲状腺功能减退症组给予不同浓度的L-T4。取妊娠17天的胎鼠、新生鼠及出生后20天幼鼠的脑样本，采用实时荧光定量PCR技术分析脑组织中Nkx2.1 mRNA的水平。
孕早期和孕晚期给予高、中、低剂量L-T4的甲状腺功能减退症组、未治疗的甲状腺功能减退症组和对照组的TT3水平分别为（0.85±0.17）、（0.81±0.18）、（0.86±0.21）、（0.85±0.20）、（0.89±0.18）、（0.85±0.20）、（0.86±0.20）、（1.08±0.07）nmol/L（F=4.08，P<0.01）；各组TT4水平分别为（0.43±0.16）、（0.39±0.11）、（0.39±0.13）（0.43±0.17）、（0.51±0.19）、（0.43±0.16）、（0.41±0.15）、（39.43±14.16）nmol/L（F=31.99，P<0.01）；各组FT3水平分别为（3.29±0.61）、（3.29±0.61）、（3.24±0.61）、（3.28±0.63）、（3.31±0.59）、（3.28±0.50）、（3.24±0.49）、（4.93±0.46）pmol/L（F=5.79，P<0.01）；各组FT4水平分别为（3.38±0.80）、（3.31±0.67）、（3.29±0.73）、（3.27±0.71）、（3.48±0.81）、（3.56±0.66）、（3.29±0.61）、（27.29±4.53）pmol/L（F=26.34，P<0.01）。未治疗的甲状腺功能减退症组在妊娠第17天Nkx2.1 mRNA表达（9.15×10-5±9.17×10-5）低于对照组（65.1×10-5±40.90×10-5）（t=66.224，P<0.05）；新生鼠中未治疗的甲状腺功能减退症组Nkx2.1 mRNA表达（3.16×10-5±0.142×10-5）低于对照组（55.6×10-5±51.05×10-5）（t=102.225，P<0.05）；出生后20天未治疗的甲状腺功能减退症组Nkx2.1 mRNA表达（8.09×10-5±8.21×10-5）低于对照组（13.9×10-5±7.43×10-5）（t=9.235，P<0.05）。孕早期给予中等剂量L-T4的甲状腺功能减退症组Nkx2.1 mRNA在妊娠第17天、新生鼠及出生后20天呈下降趋势（57.1×10-5±22.90×10-5）、（30.8×10-5±27.20×10-5）、（17.1×10-5±0.623×10-5）（F=13.394，P<0.01）。孕早期给予中等剂量L-T4的甲状腺功能减退症组在妊娠第17天、新生鼠及产后20天各时期Nkx2.1 mRNA表达最接近对照组（t值分别为0.225、0.336、0.345，P值均>0.05）。
同源框基因Nkx2.1 mRNA表达差异与甲状腺激素水平密切相关。
