Background: Thyroid hormones have extensive effects on differentiation, development, and growth of different organs. Effect of the administration of PTU in pregnant and lactating rats on isolated aorta response of their adult off-springs has been investigated. Materials and methods: Three groups of female rats were selected. In the first group, (fetal group), observation of vaginal plug after mating was considered as the first day of pregnancy, and then PTU was added to their drinking water until the end of gestational period. In the second group, PTU was added to the drinking water of female rats from the time of labor for 25 days postpartum, (neonatal group). The third group was the control group which consumed only drinking water. In all three groups total‏ thyroxine (tT4), free thyroxine (fT4), total triiodothyronine (tT3), free triiodothyronine (fT3) and TSH were measured in the sera obtained from the mothers, immediately after discontinuing the drug. Results: Levels of the above mentioned hormones, (except TSH), in fetal and neonatal groups were significantly lower than control group (p<0.05) TSH in fetal and neonatal groups was significantly higher than controls, (p<0.001). After two months the adult off springs were anesthetized, dissected and isolated aorta response was examined against KCl and phenylephrine. Results of this study indicated that responsiveness of aorta in fetal group was significantly decreased compared to the control group (p<0.05), but neonatal group had no significant difference with the control group. Conclusion: Hypothyroidism in fetal period has significant effects on differentiation and development of vascular bed, (aorta), in a way that can be still observed during adulthood.

Keywords: Hypothyroidism, Fetal, Neonatal aorta response, Rat, Propylthiouracil, Pregnancy

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