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Figure 8 The effects of genistein on calcium current and contraction of isolated guinea-pig cardiac myocytes. (A) Averaged traces from a representative cell on repetitive step depolarizations from a holding potential of –40 mV to 0 for 400 ms. (i) Control in normal Tyrode, (ii) after 1 min stabilization in 2 µM genistein, (iii) after washout in normal Tyrode and a period of action potential stimulation under current clamp. (B) (i) Current-voltage and (ii) contraction-voltage relationships in normal Tyrode (open circle) and 2 µM genistein (solid circle) with step depolarizations of 400 ms from a holding potential of –40 mV (n = 9 unless indicated otherwise). (C) Dose-response relationships for (i) L-type calcium current and (ii) contraction after 90 s in varying concentrations of genistein (n indicated for each bar). In all cases, data are expressed as mean ± SEM. * indicates p < 0.05; ** indicates p < 0.01; *** indicates p < 0.001 compared with control.
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