Figure 6.

Loss of KNa1.2 impacts whole heart substrate choice under stress. A) Cardiac function data (heart rate × pressure product, RPP) for isolated perfused hearts from WT or Kcnt2^−/− mice, perfused with Krebs-Henseleit (KH) buffer containing palmitate as the sole metabolic substrate. Bar below the traces indicates duration of 100 nM isoproterenol infusion. Graph shows RPP as a percentage of the average baseline value for 1 min. before isoproterenol infusion. Inset: comparison of the peak response to isoproterenol under this substrate condition (palmitate only, blue). Adjacent inset (right): the peak response to isoproterenol from a separate series of perfusions in which the KH buffer contained both palmitate and glucose as substrates (purple). Data are means ± sem (n = 7). *P < 0.05 between genotypes. B) EKG parameters obtained in vivo from tribromoethanol-anesthetized WT and Kcnt2^−/− mice. R–R′, distance between R waves of each beat (i.e., 1/HR); P, P-wave duration; P–R, interval between P and R waves; QRS₁ & QRS₂, diameter of QRS complex (different calculation algorithms); Q–T, interval between Q and peak of T wave; Q–T_max, interval between Q and end of T wave; Q–T_corr, QT interval corrected for heart rate. Data are mean ± sd (n = 4–5 animals).