Membrane depolarization, elevated Ca(2+) entry, and gene expression in cerebral arteries of hypertensive rats

Elevated intracellular Ca(2+) ([Ca(2+)](i)) has been implicated in contractile and phenotypic changes in arterial smooth muscle during hypertension. This study examined the role of membrane potential and [Ca(2+)](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 approximately 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 Ca(2+) was elevated in cerebral arteries from hypertensive animals, an effect reversed by diltiazem, a blocker of voltage-dependent Ca(2+) channels. This depolarization-induced increase in [Ca(2+)](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 Ca(2+) channel blocker nisoldipine. This study provides the first information linking altered Ca(2+) handling to changes in gene expression in cerebral arteries during hypertension.