Membrane depolarization, elevated Ca2+ entry, and gene expression in cerebral arteries of hypertensive rats

Abstract

Elevated intracellular Ca2+([Ca2+]i) has been implicated in contractile and phenotypic changes in arterial smooth muscle during hypertension. This study examined the role of membrane potential and [Ca2+]i in altered gene expression in cerebral arteries of a rat (Dahl) genetic model of salt-sensitive hypertension. Cerebral arteries from hypertensive animals (Dahl salt-sensitive) exhibited a tonic membrane depolarization of ∼15 mV compared with normotensive (Dahl salt-resistant) animals. Consistent with this membrane depolarization, voltage-dependent K+currents were decreased in cerebral artery myocytes isolated from hypertensive animals. Arterial wall Ca2+ was elevated in cerebral arteries from hypertensive animals, an effect reversed by diltiazem, a blocker of voltage-dependent Ca2+ channels. This depolarization-induced increase in [Ca2+]i was associated with increased activation of the transcription factor, cAMP response element binding protein, and increased expression of the immediate early gene c-fos, both of which are reversed by acute exposure to the voltage-dependent Ca2+ channel blocker nisoldipine. This study provides the first information linking altered Ca2+handling to changes in gene expression in cerebral arteries during hypertension.