Fig. 5. SR Ca²⁺ content in burbot ventricular myocytes. Representative recordings of inward Na⁺-Ca²⁺ exchange currents (I_NCX) in response to caffeine (10 mmol l^-1, designated by the white bar) in burbot ventricular myocytes at 4°C (A) and 11°C (B). The insets show the corresponding time integral of I_NCX at each temperature. (C) Mean values ± s.e.m.; N=119 myocytes at 4°C and 20 myocytes at 11°C, respectively. NS, values were not significantly different (Student's t-test, P>0.05). SR Ca²⁺ content is expressed as the charge carried by the integral (pC) normalized to cell capacitance (pF). In the text, values for charge (pC) are converted into µmol Ca²⁺ (see Materials and methods) to facilitate comparisons with literature values.