Decreased function of voltage-gated potassium channels contributes to augmented myogenic tone of uterine arteries in late pregnancy

function of voltage-gated potassium channels contributes to augmented myogenic tone of uterine arteries in late pregnancy. Am J Physiol Heart Circ Physiol 294: H272–H284, 2008. First published November 2, 2007; doi:10.1152/ajpheart.00216.2007.—Increased pressure-induced (myo-genic) tone in small uteroplacental arteries from late pregnant (LP) rats has been previously observed. In this study, we hypothesized that this response may result from a diminished activity of vascular smooth muscle cell (SMC) voltage-gated delayed-rectifier K (Kv) channels, leading to membrane depolarization, augmented Ca2 in-flux, and vasoconstriction (tone). Elevation of intraluminal pressure from 10 to 60 and 100 mmHg resulted in a marked, diltiazem-sensitive rise in SMC cytosolic Ca2 concentration ([Ca2]i) associ-ated with a vasoconstriction of uteroplacental arteries of LP rats. In contrast, these changes were significantly diminished in uterine arter-ies from nonpregnant (NP) rats. Gestational augmentation of pressure