Abstract
ObjectiveCa2+ influx through voltage‐dependent Ca2+ channels regulates vascular contraction and remodeling. However, the role of T‐type Ca2+ channels (TCCs) has remained unknown in the ductus arteriosus (DA).Methods and Results 1) α1G, a TCC subtype, was significantly up‐regulated in rat neonatal DA tissues at birth and in DA smooth muscle cells (SMCs) that were exposed to oxygen. α1G was localized predominantly to the region of intimal thickening in fetal DA at term and to the central core of neonatal DA at birth. 2) α1G over expression promoted SMC migration by 164% relative to control (n=7, p<0.01). α1G‐specific siRNAs inhibited SMC migration by 60% relative to negative siRNA (n=8, p<0.01). A highly selective TCC blocker, R(−)‐efonidipine, suppressed SMC migration by 62% relative to control (n=5, p<0.01). 3) A prostaglandin E receptor EP4 agonist potently promoted physiological intimal thickening (Yokoyama et al. J Clin Invest 2006). Intimal‐media ratio of DA stimulated by EP4 was decreased by 60% in the presence of R(−)‐efonidipine (n=5, p<0.01). 4) R(−)‐efonidipine significantly attenuated oxygen‐induced vasoconstriction in a dose‐dependent manner.ConclusionTCC, especially α1G, regulates SMC migration, neointimal formation, and oxygen‐induced vascular contraction in rat DA.
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