Figure 1.

Acute hyperglycaemia induces action potential changes dependent on CaMKII. (A) High glucose (30 mM, 6 min) induced action potential (AP) changes in murine ventricular and rabbit atrial and ventricular cardiomyocytes. Representative traces are shown at 1 Hz steady-state pacing. Paired data on AP duration at 90% repolarization (APD₉₀) are shown in insets. Tachypacing-induced APD₉₀ alternans is shown below (S and L refer to short and long APD₉₀, respectively). (B) CaMKII inhibition using the selective inhibitor AIP (1 μM) attenuated high glucose effects. (C) APD₉₀ at 1 Hz steady-state pacing and the magnitude of the tachypacing-induced APD₉₀ alternans (at 10 Hz in mouse and at 5 Hz in rabbit). (D) Representative Poincaré plots of 50 consecutive APD values. Insets show short-term variability (STV) of APD₉₀ at 1 Hz pacing. (Murine ventricular cells, control: n = 16 cells from nine animals at 1 Hz and n = 15 cells from eight animals at 10 Hz; AIP: n = 13 cells from six animals at both 1 Hz and 10 Hz pacing. Rabbit atrial cells, control: n = 12 cells from six animals at 1 Hz and n = 7 cells from four animals at 5 Hz; AIP: n = 8 cells from three animals at 1 Hz and n = 6 cells from three animals at 5 Hz pacing. Rabbit ventricular cells, control: n = 15 cells from seven animals at both 1 Hz and 5 Hz pacing; AIP: n = 12 cells from five animals at both 1 Hz and 5 Hz pacing.) Nested t-test; NS, non-significant; *P < 0.05, **P < 0.01, ***P < 0.001.