Effects of thyroid hormone on the expression of homeobox gene Nkx6.1 in the cerebrum tissue of offspring of hypothyroidism rat

Abstract

Objective To explore the effects of thyroid hormone on the expression of homeobox gene Nkx6.1 in offspring of hypothyroidism rats and the relationship between gene expression and hormone level by supplying their hypothyroidism pregnant mother with thyroid hormone. Method A total of 240 Wistar rats were half nude and half female. Female rats were randomly divided into eight groups: control, hypothyroidism group, hypothyroidism groups which were supplied with thyroid hormone in high, medium and low dosage in early stage(1- 17 d) and in late stage( 18 - 20 d). According to 100 grams of body weight, the concentration of thyroid hormone 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 normal control group was given KIO_3 solution and the other groups were given deionized water. After three months female rats were mated with male rats. The content of Nkx6.1 mRNA in brain tissue of 17-day fetal rats, new-born and 20- day old offspring by real-time fluorescence quantitative PCR techniques. Results①A rat model of hypothyroidism was successfully established, there were statistical significance between 8 groups in TT_3,TT_4,FT_3,FT_4(F=4.08,31.99,5.79,26.34, all P 0.05), while between the other 5 groups which were supplied with thyroid hormone and normal control group had significant difference(all P < 0.01 ) in the above three time points.⑦Multiple comparison of early stage groups which were supplied with thyroid hormone showed that the expression of Nkx6.1 mRNA had significant difference(all P < 0.01) between high, low dosage groups and medium group in 17-day fetal rats, new-bern and 20-day offspring(all P< 0.01). ⑧Multiple comparison of late stage groups supplied with thyroid hormone showed that old offspring and between high dosage groups and low dosage groups in 17-day fetal rats and 20-day the expression of Nkx6.1 mRNA had significant difference(all P < 0.01 ) between three groups in new-bern and 20- day old offspring. Conclusion The expression of Nkx6.1 in rats offspring is highly related to the supply dosage and supply time of thyroid hormone in hypothyroidism pregnant rats. Key words: Hypothyroidism; Homeobex gene; Thyroxine; Real-time fluorescence quantitative PCR