Ca2+ Waves and Intracellular Ca2+ Concentration in Guinea Pig and Rat Myocytes

We measured [Ca2+]i of guinea pig and rat myocytes with Ca2+ waves, using fura-2 fluorescence image processing. In guinea pig myocytes, Ca2+ waves were absent during the control perfusion period, but could be induced by the addition of strophanthidin (100μM) or sodium cyanide (NaCN: 2mM) to the perfusate. The [Ca2+]i increased from the control values of 69±5nM and 46±2nM, to 263±9 (p<0.05 vs. control) nM and 225±20 (p<0.05) nM, respectively, when cells exhibited Ca2+ waves. Although 13% (16 of 121) of the rat myocytes displayed Ca2+ waves during the control perfusion, the [Ca2+]i with Ca2+ waves (56±9nM) did not differ from [Ca2+]i in the absence of Ca2+ waves (54±3nM). Ca2+ waves were induced by the perfusion with a high Ca2+ solution (24.5μM) or NaCN (2μM), and [Ca2+]i increased from the control values of 67±11nM and 74±5nM, to 231±41 (p