Use of the Ca-Shortening Curve to Estimate the Myofilament Responsiveness to Ca2+ in Tetanized Rat Ventricular Myocytes

The Journal of Physiological Sciences

Makoto Kawai³  Masato Konishi¹  Yoichiro Kusakari²  Kenichi Hongo³  Satoshi Kurihara² 

[1] Department of Physiology (I), Tokyo Medical University;Department of Physiology (II), The Jikei University School of Medicine;Division of Cardiology, The Jikei University School of Medicine

关键词: calcium (cellular);    contractile function;    inotropic agents;    myocytes;    second messengers;   

DOI  :  10.2170/physiolsci.RP003706

学科分类：生理学

来源: Springer

【 摘 要 】

References(29)Cited-By(1)We previously estimated the myofilament responsiveness to Ca2+ in isolated intact ventricular myocytes, using the steady-state relationship between cytosolic Ca2+ concentration ([Ca2+]i) and cell-shortening during tetanus (Ca-L trajectory). This method was useful and easy; however, it could not be used for a high dose of Ca sensitizer because the instantaneous plots after the application of Ca sensitizer did not make a fixed point of shortening (we used 5% shortening). Therefore we must produce another method to investigate Ca2+ responsiveness. For an estimation of a wider range of the Ca-L trajectory, we fitted the Ca-L trajectory data with the Hill equation to construct the Ca-shortening curve. To fit this curve, we measured the maximal shortening, which was on average 31.6%. The value of [Ca2+]i to produce the half-maximal shortening (Ca50) was dose-dependently decreased by EMD57033 (sensitization). Either isoproterenol or 3-isobutyl-1-methylxanthine increased Ca50 (desensitization) with a concomitant increase in intracellular c-AMP. EMD57439, a selective PDE-III inhibitor, did not significantly increase the c-AMP concentration and produced little change in Ca50. These results are in agreement with previous reports with skinned or intact multicellular preparations. The Ca-shortening curve constructed in intact cardiac myocytes can be used to estimate the myofibrillar responsiveness to Ca2+ in a wide range of [Ca2+]i.

【 授权许可】

Unknown