Thyroid hormone receptor-α and vascular function

Makino A, Wang H, Scott BT, Yuan JXJ, Dillmann WH. Thyroid hormone receptor-alpha and vascular function. Am J Physiol Cell Physiol 302: C1346-C1352, 2012. First published February 8, 2012; doi:10.1152/ajpcell.00292.2011.-Thyroid hormone (TH) treatment exerts beneficial effects on the cardiovascular system: it lowers cholesterol and LDL levels and enhances cardiac contractile function. However, little is known about the effect of TH on vascular function or the functional role of TH receptors (TRs) in the regulation of vascular tone. We have investigated the contribution of TRs to vascular contractility in the heart. Among different TR subtype-specific knockout (KO) mice, vascular contraction was significantly enhanced in coronary arteries isolated from TR alpha KO compared with wild-type mice, while chronic TH treatment significantly attenuated coronary vascular contraction. We found that TR alpha is the predominant TR in mouse coronary smooth muscle cells (SMCs). Coronary SMCs isolated from TR alpha KO mice exhibited a significant decrease in K+ channel activity, whereas TH treatment increased K+ channel activity in a dose-dependent manner. These data suggest that TR alpha in SMCs has prominent effects on regulation of vascular tone and TH treatment helps decrease coronary vascular tone by increasing K+ channel activity through TR alpha in SMCs.