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This Article Full Text Full Text (PDF) All Versions of this Article: 297/5/H1820    most recent 00326.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nystoriak, M. A. Articles by Wellman, G. C. PubMed PubMed Citation Articles by Nystoriak, M. A. Articles by Wellman, G. C.

Ca_v1.2 splice variant with exon 9* is critical for regulation of cerebral artery diameter

Departments of ¹Pharmacology and Surgery, ²Division of Neurological Surgery, University of Vermont, College of Medicine, Burlington, Vermont

Submitted April 3, 2009 ; accepted in final form August 24, 2009

L-type voltage-dependent Ca²⁺ channels (VDCCs) are essential for numerous processes in the cardiovascular and nervous systems. Alternative splicing modulates proteomic composition of Ca_v1.2 to generate functional variation between channel isoforms. Here, we describe expression and function of Ca_v1.2 channels containing alternatively spliced exon 9* in cerebral artery myocytes. RT-PCR showed expression of Ca_v1.2 splice variants both containing (₁C_9/9*/10) and lacking (₁C_9/10) exon 9* in intact rabbit and human cerebral arteries. With the use of laser capture microdissection and RT-PCR, expression of mRNA for both ₁C_9/9*/10 and ₁C_9/10 was demonstrated in isolated cerebral artery myocytes. Quantitative real-time PCR revealed significantly greater ₁C_9/9*/10 expression relative to ₁C_9/10 in intact rabbit cerebral arteries compared with cardiac tissue and cerebral cortex. To demonstrate a functional role for ₁C_9/9*/10, smooth muscle of intact cerebral arteries was treated with antisense oligonucleotides targeting ₁C_9/9*/10 (₁C_9/9*/10-AS) or exon 9 (₁C-AS), expressed in all Ca_v1.2 splice variants, by reversible permeabilization and organ cultured for 1–4 days. Treatment with ₁C_9/9*/10-AS reduced maximal constriction induced by elevated extracellular K⁺ ([K⁺]_o) by 75% compared with ₁C_9/9*/10-sense-treated arteries. Maximal constriction in response to the Ca²⁺ ionophore ionomycin and [K⁺]_o EC₅₀ values were not altered by antisense treatment. Decreases in maximal [K⁺]_o-induced constriction were similar between ₁C_9/9*/10-AS and ₁C-AS groups (22.7 ± 9% and 25.6 ± 4% constriction, respectively). We conclude that although cerebral artery myocytes express both ₁C_9/9*/10 and ₁C_9/10 VDCC splice variants, ₁C_9/9*/10 is functionally dominant in the control of cerebral artery diameter.

vascular smooth muscle; calcium channels; cerebral blood flow