Table 2:

Action potential characteristics in WT and R67Q^+/− myocytes at baseline and following isoproterenol.

Condition	RMP (mV)	dV/dTmax (V/sec)	APA (mV)	APD10 (msec)	APD50 (msec)	APD70 (msec)	APD90 (msec)
WT
2Hz	−70.91 ± 0.71	232.40 ± 15.57	117.60 ± 1.88	0.37 ± 0.03	3.36 ± 0.58	7.76 ± 1.22	35.97 ± 3.40
4Hz	−71.27 ± 1.19	244.40 ± 6.13	115.40 ± 2.06	0.40 ± 0.03	3.44 ± 0.64	8.31 ± 1.35	38.88 ± 3.86
6Hz	−71.85 ± 1.55	245.00 ± 8.55	112.30 ± 2.10	0.42 ± 0.04	3.79 ± 0.72	9.65 ± 1.62	40.66 ± 3.44
WT + ISO
2Hz	−74.66 ± 0.75*	256.10 ± 9.51	118.20 ± 1.43	0.40 ± 0.04	4.76 ± 0.77	8.94 ± 1.29	32.33 ± 2.13
4Hz	−76.51 ± 1.13*	257.90 ± 9.03	118.20 ± 1.49	0.45 ± 0.04	5.81 ± 0.77	11.46 ± 1.53	39.63 ± 1.61
6Hz	−76.49 ± 1.41	256.10 ± 10.05	115.80 ± 1.51	0.45 ± 0.05	6.21 ± 0.89	13.42 ± 1.97	42.61 ± 3.28
R67Q+/−
2Hz	−71.10 ± 0.62	268.90 ± 6.54	120.90 ± 2.30	0.54 ± 0.13	7.65 ± 3.26	18.79 ± 7.50	54.34 ± 13.92*
4Hz	−70.76 ± 0.93	268.90 ± 7.32	118.50 ± 2.20	0.55 ± 0.13	7.07 ± 2.61	17.87 ± 5.67	55.70 ± 10.02*
6Hz	−70.10 ± 1.34	261.50 ± 8.16	114.70 ± 2.03	0.59 ± 0.16	6.69 ± 2.34	19.90 ± 5.19	67.76 ± 14.12***
R67Q+/− + ISO
2Hz	−73.90 ± 1.29	264.60 ± 8.31	118.20 ± 2.92	0.74 ± 0.30	9.94 ± 3.12	18.44 ± 5.10	59.10 ± 11.76**
4Hz	−74.25 ± 1.13	264.00 ±10.59	115.90 ± 3.33	0.81 ± 0.32	10.81 ± 2.91	20.89 ± 5.01	62.81 ± 10.30***
6Hz	−72.97 ± 1.06	267.00 ± 11.35	110.50 ± 4.18	0.86 ± 0.33	11.15 ± 2.18	23.00 ± 3.26	64.38 ± 9.38***

Values are means ± SE. Resting membrane potential (RMP), dV/dT_max, action potential amplitude (APA) and action potential duration (APD) at 2, 4 and 6Hz at baseline and following isoproterenol.

^*P < 0.05,

^**P < 0.01,

and

^***P < 0.001 compared to WT.

(WT - N=4, n=7; WT + ISO – N=4, n=6; R67Q^+/− +/− ISO - N=3, n=5). Two-way repeated measures (Treatment (+/− ISO) or duration of action potential) ANOVA with post-hoc Bonferroni correction was used. Significance levels indicated are following Bonferroni correction.