Visscher M B, Lee Y C
Proc Natl Acad Sci U S A. 1972 Feb;69(2):463-5. doi: 10.1073/pnas.69.2.463.
The positive inotropic action of glucagon on the cat heart is dependent upon the extracellular Ca concentration. The inotropic effect is proportionately greater, the lower the concentration of Ca in the perfusate (above zero, at which glucagon is without significant effect). Nevertheless, Ca influx (as measured with (45)Ca) into the myocardium is not demonstrably influenced by glucagon, except at 0.09 mM Ca, where the interpretation of the effect is complicated by the fact that there is mechanical asystole at that Ca concentration in the absence of glucagon, while excitation-contraction coupling still occurs when the hormone is added. The possibility is suggested that glucagon may influence intracellular movement of Ca, even when its transmembrane movement is affected only slightly.
胰高血糖素对猫心脏的正性肌力作用取决于细胞外钙浓度。灌注液中钙浓度越低（高于零，此时胰高血糖素无显著作用），肌力作用就越大。然而，胰高血糖素对心肌的钙内流（用⁴⁵Ca测量）没有明显影响，除了在0.09 mM钙浓度时，此时效应的解释较为复杂，因为在该钙浓度下，无胰高血糖素时会出现机械性心搏停止，而添加该激素时仍会发生兴奋 - 收缩偶联。这表明即使胰高血糖素对钙的跨膜运动影响轻微，它仍可能影响钙的细胞内运动。
