Figure 5.

The effect of isoproterenol (ISO) on intracellular calcium concentration in shark ventricular myocyte. (A) Time courses of calculated rise in total intracellular calcium concentration ([Ca²⁺]_i) constructed from digital integration of the traces of I_Na-Ca envelopes shown in Fig. 4 A and B to provide and estimate of the total charge transferred, using a 3 Na⁺ to 1 Ca²⁺ exchanger stoichiometry. (B) Superimposed digitized calcium changes constructed from the currents during the 150-ms depolarizing pulse in the presence and absence of ISO. (C) Normalized [Ca²⁺]_i constructed from the records shown in B for control (CON) and ISO-exposed myocytes.