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

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-sens itive hypertension. Cerebral arteries from hypertensive animals (Dahl salt- sensitive) exhibited a tonic membrane depolarization of similar to 15 mV co mpared with normotensive (Dahl salt-resistant) animals. Consistent with thi s 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 prote in, and increased expression of the immediate early gene c-fos, both of whi ch are reversed by acute exposure to the voltage-dependent Ca2+ channel blo cker nisoldipine. This study provides the first information linking altered Ca2+ handling to changes in gene expression in cerebral arteries during hy pertension.