Impaired cyclic nucleotide-dependent vasorelaxation in human umbilical artery smooth muscle

A comparative study of the bovine carotid artery smooth muscle (BCASM)- and human umbilical artery smooth muscle (HUASM) responses to contractile and relaxant agents reveals that passive relaxations of both smooth muscle types are normal after a washout of vasoactive agents. HUASM does not exhibit active relaxation, unlike BCASM, probably due to changes induced in cyclic nucleotide-dependent kinases in HUASM. The active relaxation refractoriness may lead to the vasospasm that appears due to parturition in umbilical vasculature.