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Báo cáo khoa học: Calcium and polyamine regulated calcium-sensing receptors in cardiac tissues

Activation of a calcium-sensing receptor (Ca-SR) leads to increased intracellular calcium concentration and altered cellular activities. The expression of Ca-SR has been iden-tified in both nonexcitable and excitable cells, including neurons and smooth muscle cells. Whether Ca-SR was expressed and functioning in cardiac myocytes remained unclear. In the present study, the transcripts of Ca-SR were identified in rat heart tissues usingRT-PCRthat was further confirmed by sequence analysis. | Eur. J. Biochem. 270 2680-2688 2003 FEBS 2003 doi 10.1046 j.1432-1033.2003.03645.x Calcium and polyamine regulated calcium-sensing receptors in cardiac tissues Rui Wang1 Changqing Xu2 Weimin Zhao1 Jing Zhang1 Kun Cao1 Baofeng Yang2 and Lingyun Wu3 1 Department of Physiology University of Saskatchewan Saskatoon SK Canada department of Pathophysiology Harbin Medical University Harbin P.R. China 3Department of Pharmacology University of Saskatchewan Saskatoon SK Canada Activation of a calcium-sensing receptor Ca-SR leads to increased intracellular calcium concentration and altered cellular activities. The expression of Ca-SR has been identified in both nonexcitable and excitable cells including neurons and smooth muscle cells. Whether Ca-SR was expressed and functioning in cardiac myocytes remained unclear. In the present study the transcripts of Ca-SR were identified in rat heart tissues using RT-PCR that was further confirmed by sequence analysis. Ca-SR proteins were detected in rat ventricular and atrial tissues as well as in isolated cardiac myocytes. Anti- Ca-SR Ig did not detect any specific bands after preadsorption with standard Ca-SR antigens. An immunohistochemistry study revealed the presence of Ca-SR in rat cardiac as well as other tissues. An increase in extracellular calcium or gadolinium induced a concentration-dependent sustained increase in Ca2 i in isolated ventricular myocytes from adult rats. Spermine 1-10 mM also increased Ca2 i. Pre-treatment of cardiac myocytes with thapsigargin or U73122 abolished the extracellular calcium gadolinium or spermine-induced increase in Ca2 i. The blockade of Na Ca2 exchanger or voltagedependent calcium channels did not alter the extracellular calcium-induced increase in Ca2 i. Finally extracellular calcium gadolinium and spermine all increased intracellular inositol 1 4 5-triphosphate IP3 levels. Our results demonstrated that Ca-SR was expressed in cardiac tissue and cardiomyocytes and its function was regulated by