Table 1.

Intracellular calcium decline rate constant (τ) in aged and adult rat hearts

	N	Base	Mid	Apex	P
Adult rat
Baseline, ms	8	71±5	72±5	73±5	NS
H2O2, ms	8	80±7	82±8	83±8	NS
P		<0.05	<0.05	<0.05
Aged rat
Baseline, ms	14	84±6‡	76±7‡	74±5‡	<0.05
H2O2, ms	8	110±8‡	96±8‡	94±10‡	<0.01
P		<0.01	<0.01	<0.01

Values are means ± SD; N, number of rats. Repeated-measures ANOVA comparison of intracellular calcium decline rate at different left ventricular (LV) sites during pacing at a cycle length of 200 ms are shown. *P < 0.05, significant difference between adult and aged hearts at all LV sites both at baseline and after H₂O₂. †P < 0.01, significant regional differences exist in the aged hearts between the base and the mid- and the apex of LV both at baseline and after H₂O₂. No differences are seen between mid- and apical sites at baseline and after H₂O₂ in the aged hearts. NS, not significant.