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. 2000 Jun 1;525(Pt 2):483–498. doi: 10.1111/j.1469-7793.2000.t01-1-00483.x

Figure 9. Cellular electrophysiological parameters as a function of age.

Figure 9

Parameter values of control (○) and CSQ (•) myocytes and the respective linear regression lines for control (dashed) and CSQ (continuous) myocytes. A, cell capacitance increased significantly with age both in control and CSQ myocytes. Control: r = 0.51, P < 0.0001, 101 myocytes from 26 hearts vs. CSQ: r = 0.60, P < 0.0001, 109 myocytes from 22 hearts. B, action potential duration (APD90) increased only in CSQ myocytes. Control: r =−0.02, P = 0.89, 24 myocytes from 9 hearts vs. CSQ: r = 0.57, P < 0.01, 23 myocytes from 6 hearts. C, Ito was downregulated in young CSQ mice and decreased further with age. Control: r =−0.19, P = 0.25, 39 myocytes from 10 hearts vs. CSQ: r =−0.62, P < 0.0001, 36 myocytes from 9 hearts. D, the sustained outward K+ current (Isustained) increased significantly with age in control myocytes, but decreased significantly in CSQ myocytes. Control: r = 0.51, P < 0.001, 39 myocytes from 10 hearts vs. CSQ: r =−0.67, P < 0.0001, 36 myocytes from 9 hearts. E, IK1 remained unchanged in control myocytes, but decreased in CSQ myocytes. Control: r =−0.08, P = 0.69, 23 myocytes from 9 hearts vs. CSQ: r =−0.50, P < 0.05, 18 myocytes from 6 hearts. F, basal ICa (ICa,basal) decreased significantly with age in control myocytes, but remained unchanged in CSQ myocytes. Control: r =−0.62, P < 0.05, 11 myocytes from 3 hearts vs. CSQ: r =−0.26, P = 0.37, 14 myocytes from 7 hearts. G, maximally activated ICa (ICa,activated; 200 μmol l−1 8-Br-cAMPi) decreased significantly with age in both control and CSQ myocytes. Control: r =−0.45, P < 0.05, 21 myocytes from 6 hearts vs. CSQ: r =−0.67, P < 0.001, 20 myocytes from 6 hearts. H, no significant age-dependent changes in INa were present (GNa, Na+ channel conductance). Control: r = 0.29, P = 0.15, 24 myocytes from 5 hearts vs. CSQ: r =−0.22, P = 0.22, 31 myocytes from 6 hearts. In C and D, currents were measured at 40 mV; in E, currents were measured at −100 mV.