Background
The effect of propylthiouracil (PTU) administration to pregnant and lactating rats on isolated aorta contractility of their adult offspring was investigated.
Material and Method
Three groups of female rats were selected; in the fetal group (FG), PTU was added to their drinking water during gestation; in the neonatal group (NG), PTU was added to the mothers' drinking water for 25 days after delivery; untreated rats were controls (CG). Thyroid hormone concentrations were measured in the sera of the mothers and their adult offspring. Aortic contractility of the offspring was measured with an isometric transducer in the presence of different concentrations of potassium chloride (KCl) and phenylephrine.
Results
The mothers were hypothyroid at the time of PTU cessation. Thyroid hormone levels in offspring were not significantly different from those of controls except for TSH, which was significantly (p<0.05) higher in the FG offspring. Recorded tension in FG offspring with 5, 10, 20, 40, and 60 mmol/l KCl were 0.21+/-0.02, 0.75+/-0.07, 1.07+/-0.07, 1.38+/-0.08, and 1.5+/-0.09 g/mm2, respectively, significantly (p<0.05) lower than the control values (0.43+/-0.05, 1.19+/-0.17, 1.76+/-0.23, 2.06+/-0.22, 2.5+/-0.09). Aortic contractility with 10-8, 10-7, and 10-6 mmol/l of phenylephrine in the FG offspring were 0.6+/-0.13, 1.4+/-0.15, and 1.8+/-0.15 g/mm2, significantly lower than control values (1.24+/-0.19, 2.3+/-0.25, 2.6+/-0.28). Contractility of the NG aorta did not differ significantly from controls.
Conclusions
Hypothyroidism during the fetal period has significant effects on the differentiation and development of the vascular bed (aorta), the long-term effects of which can still be observed during adulthood.

Keywords: Propylthiouracil - pharmacology, Pregnancy, Potassium Chloride - pharmacology, Phenylephrine - pharmacology, Maternal Exposure, Muscle Contraction - drug effects, Lactation, Aorta - physiology, Administration, Oral, Thyroid Hormones - blood