Novel role for K+-dependent Na+/Ca2+ exchangers in regulation of cytoplasmic free Ca2+ and contractility in arterial smooth muscle.
نویسندگان
چکیده
Cytoplasmic free Ca2+ ([Ca2+]cyt) is essential for the contraction and relaxation of blood vessels. The role of plasma membrane Na+/Ca2+ exchange (NCX) activity in the regulation of vascular Ca2+ homeostasis was previously ascribed to the NCX1 protein. However, recent studies suggest that a relatively newly discovered K+-dependent Na+/Ca2+ exchanger, NCKX (gene family SLC24), is also present in vascular smooth muscle. The purpose of the present study was to identify the expression and function of NCKX in arteries. mRNA encoding NCKX3 and NCKX4 was demonstrated by RT-PCR and Northern blot in both rat mesenteric and aortic smooth muscle. NCXK3 and NCKX4 proteins were also demonstrated by immunoblot and immunofluorescence. After voltage-gated Ca2+ channels, store-operated Ca2+ channels, and Na+ pump were pharmacologically blocked, when the extracellular Na+ was replaced with Li+ (0 Na+) to induce reverse mode (Ca2+ entry) activity of Na+/Ca2+ exchangers, a large increase in [Ca2+]cyt signal was observed in primary cultured aortic smooth muscle cells. About one-half of this [Ca2+]cyt signal depended on the extracellular K+. In addition, after the activity of NCX was inhibited by KB-R7943, Na+ replacement-induced Ca2+ entry was absolutely dependent on extracellular K+. In arterial rings denuded of endothelium, a significant fraction of the phenylephrine-induced and nifedipine-resistant aortic or mesenteric contraction could be prevented by removal of extracellular K+. Taken together, these data provide strong evidence for the expression of NCKX proteins in the vascular smooth muscle and their novel role in mediating agonist-stimulated [Ca2+]cyt and thereby vascular tone.
منابع مشابه
Novel role for K -dependent Na /Ca exchangers in regulation of cytoplasmic free Ca and contractility in arterial smooth muscle
Hui Dong, Yanfen Jiang, Chris R. Triggle, Xiaofang Li, and Jonathan Lytton Division of Gastroenterology, Department of Medicine, University of California, San Diego School of Medicine, San Diego, California; and Department of Pharmacology and Therapeutics and Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
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ورودعنوان ژورنال:
- American journal of physiology. Heart and circulatory physiology
دوره 291 3 شماره
صفحات -
تاریخ انتشار 2006