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Figure 5 (A) Changes in the contractile responses of isolated left ventricular strips of uremic (SNX) and sham-operated (SOP) rats to cumulative concentrations of isoprenaline. Control values: SNX, 4.5 ± 0.27 (n = 15); SOP, 3.5 ± 0.24 mN (n = 9). (B) Changes in the calcium-induced positive inotropic response in SOP and SNX rats. Control values: SNX, 2.3 ± 0.3 mN (n = 15); SOP, 1.67 ± 0.2 mN (n = 9). (C) Decrease in contractile force in ventricular strips prestimulated with 3 µmol/liter forskolin by cumulative concentrations of carbachol in SOP (n = 3) and SNX (n = 3) rats. Control values after preconstriction with 3 µmol/liter forskolin: SNX, 5.7 ± 0.4 mN (n = 3); SOP, 6.5 ± 0.7 mN (n = 3). All values are given as means ± SEM. Significant differences between both groups are indicated by an asterisk (* = p < 0.05; ** = p < 0.01; *** = p < 0.001).