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. 2020 Mar 20;318(6):H1357–H1370. doi: 10.1152/ajpheart.00481.2019

Fig. 3.

Fig. 3.

Reduced synapse-associated protein 97 (Sap97) expression lengthens the cardiac action potential (AP), reduces K+ currents, and enhances Na+ current (INa) A and B: action potentials recorded at 1 Hz in isolated Sap97-knockout (KO) mouse ventricular myocytes (red) demonstrate significantly longer AP duration (APD) 30,50 and 90% repolarization [N = 3, n = 7 wild-type (WT); N = 3, n = 13 Sap97-KO]. Horizontal bars represent means; vertical bars, SD. C and D: Sap97-KO cells frequently demonstrated early afterdepolarizations absent in WT cells. E–G: current-voltage (I-V) relationships for inward rectifier (IK1,), transient outward K+ (Ito,), and the fast INa currents. Peak inward IK1 (at test voltage −120 mV) and peak outward Ito (at test voltage +60 mV) were reduced 20 and 54%, respectively (in pA/pF; IK1, −16.38 ± 1.14 WT, 13.25 ± 0.76 Sap97-KO; N = 3,3; n = 7,9. *P = 0.036; t-test; Ito, 43.68 ± 3.91 WT, 19.96 ± 2.48 Sap97-KO; N = 3,5; n = 10,20; #P = 0.027; t-test). Peak INa (at a test voltage −55mV) was upregulated ~47% (in pA/pF; −32.52 ± 4.60 WT, −47.54 ± 4.47 Sap97-KO; N = 3,4; n = 10,10; $P = 0.0193; t-test). Vm, membrane potential.