Gestational hypothyroidism-induced changes in L-type calcium channels of rat aorta smooth muscle and their impact on the responses to vasoconstrictors

Objective(s): Thyroid hormones play an essential role in fetal growth and maternal hypo-thyroidism which leads to cardiovascular deficiency in their offspring.  Considering this, we intended to investigate the impact of gestational hypothyroidism on offspring vascular contractibility and possible underlying mechanisms. Materials and Methods: Hypothyroidism was induced in female rats by administration of ۶-n-propyl-۲-thiouracil in drinking water (۰.۰۲%) till delivery. The offspring aorta smooth muscle (without endothelium) contractile response to KCl (۱۰-۱۰۰ mM), KCl in the presence of nifedipine (۱۰-۴-۱۰-۱ µM), phenylephrine (۱۰-۹-۱۰-۶ M) and finally, phenylephrine and caffeine ۱۰۰ mM in Ca۲+-free Krebs were measured.    Results: KCl and phenylephrine-induced contractions were considerably lower in gestational hypothyroid (GH) than euthyroid offspring. GH responded to nifedipine with less sensitivity than control. The GH and control groups produced almost equal contraction in respond to phenylephrine and caffeine in Ca۲+-free Krebs.  Conclusion: This study suggests that in hypothyroid offspring L-type Ca۲+ channels are less functional, while intracellular Ca۲+ handling systems are less modified by low levels of maternal thyroid hormones.

Keywords:

Aorta smooth muscle , Gestational hypothyroidism , L-type calcium channel