Skomedal T, Schiander I, Aass H, Osnes J B
Department of Pharmacology, University of Oslo, Norway.
Acta Physiol Scand. 1987 Nov;131(3):347-53. doi: 10.1111/j.1748-1716.1987.tb08249.x.
The qualitative characteristics of the inotropic response to increase in extracellular calcium (Cao) were studied in isolated, electrically driven, isometrically contracting rat papillary muscles. All experiments were done in the presence of adrenergic receptor blockers. Cao was increased in a cumulative way by exchanging a small fraction of the incubation solution with a corresponding solution with higher calcium concentration (8 mmol l-1). At any Cao level there was an almost proportional increase in parameters describing different parts of the contraction-relaxation cycle as compared with results at the preceding lower Cao level. Time to peak tension was prolonged at high compared with low Cao levels. The response to increased Cao was very similar to the cyclic AMP (cAMP)-independent inotropic response elicited through activation of alpha-adrenergic receptors (alpha-type response, Skomedal et al. 1982) and strikingly different from the cAMP-dependent inotropic response elicited, for example, through activation of beta-adrenergic receptors (beta-type response, Skomedal et al. 1982). As the inotropic response to increased Cao is known to be cAMP-independent (Dönges et al. 1977), the present results demonstrate the interrelationship between the regulatory function(s) and the direct effector function(s) of calcium in the myocardium.
在分离的、电驱动的、等长收缩的大鼠乳头肌中，研究了细胞外钙（Cao）增加时变力反应的定性特征。所有实验均在肾上腺素能受体阻滞剂存在的情况下进行。通过用高钙浓度（8 mmol l-1）的相应溶液交换一小部分孵育溶液，以累积方式增加Cao。与之前较低Cao水平时的结果相比，在任何Cao水平下，描述收缩-舒张周期不同部分的参数几乎成比例增加。与低Cao水平相比，高Cao水平时达到峰值张力的时间延长。对Cao增加的反应与通过激活α-肾上腺素能受体引发的不依赖环磷酸腺苷（cAMP）的变力反应非常相似（α型反应，Skomedal等人，1982年），与例如通过激活β-肾上腺素能受体引发的依赖cAMP的变力反应（β型反应，Skomedal等人，1982年）明显不同。由于已知对Cao增加的变力反应不依赖cAMP（Dönges等人，1977年），本研究结果证明了心肌中钙的调节功能和直接效应功能之间的相互关系。
