Fig 1.
Morphological and electrophysiological changes in transverse aortic banding (TAB) vs. sham operated mice.
A) Representative parasternal long axis echocardiographic images of the ventricles of sham and TAB operated mice. B) Summary data of left ventricular ejection fraction (**p<0.01 vs. sham). C) Representative action potentials recorded in isolated ventricular cardiomyocytes from sham and TAB mice. D) Summary data of action potential duration in isolated ventricular myocytes of sham and TAB mice (**p<0.01 vs. sham). APD50, APD75, APD90: action potential duration at 50%, 75% and 90% repolarization, respectively. Em: membrane potential.
Fig 2.
CaMKII is activated in ventricles of hearts following transverse aortic banding.
A) Representative western blots of phosphorylated CaMKII (P-CaMKII), oxidized CaMKII (Ox-CaMKII), total CaMKII (T-CaMKII) and GAPDH in ventricles of sham and TAB mice as labelled by whole-heart biotinylation. B) Summary of P-CaMKII, Ox-CaMKII and T-CaMKII quantification from western blots in ventricles of sham and TAB mice (*p<0.05, **p < .01 vs. sham).
Fig 3.
KATP channel surface expression is down-regulated in ventricles of hearts after transverse aortic banding.
A) Representative western blots of the KATP Kir6.2 subunit and the sodium-potassium pump (Na+-K+ pump) from the biotinylated membrane fraction of ventricular tissue from isolated hearts of sham and TAB mice. B) Summary of ventricular membrane Kir6.2 expression normalized to Na+-K+ pump expression in hearts of sham and TAB mice (*p<0.05 vs. sham). C) Representative current profiles of isolated left ventricular myocytes before and after application of the KATP channel activators, pinacidil (PIN, 100 μM) and 2,4-dinitrophenol (DNP, 200 μM). D) Summary of KATP channel current density (after-before KATP channel activations) from isolated ventricular cardiomyocytes of sham and TAB mice (**p<0.01 vs. sham).
Fig 4.
Dynamic downregulation of KATP channel current density is blunted in ventricular cardiomyocytes of TAB mice.
A) Representative tracings of pinacidil (PIN, 100 μM)- and 2,4-dinitrophenol (DNP, 200 μM)-stimulated KATP channel current density in response to isoproterenol (ISO, 1 μM). B) Summary of percent inhibition of pinacidil and DNP-stimulated KATP channel current density by isoproterenol (1 μM) in isolated cardiomyocytes of sham and TAB mice (**p<0.01 vs. sham).
Fig 5.
Monophasic action potential duration shortening is blunted in failing hearts.
Monophasic action potentials were measured from a single left ventricular epicardial position in isolated hearts from TAB and sham mice before and during exposure to hypoxia or abrupt heart rate acceleration from 400 beats per minute (bpm) to 667 bpm (150 msec cycle length to 90 msec cycle length) driven by pacing. A) Representative normalized monophasic action potentials at baseline (solid lines) and in response to hypoxia (dotted lines) from hearts of sham (left panel) and TAB (right panel) mice. A horizontal line designates the point at which monophasic action potential duration at 90% repolarization (MAPD90) was measured. B) Summary of MAPD90 shortening (left), half-time (t1/2) of MAPD90 shortening (middle), and rate of MAPD90 shortening (right) in hearts from sham and TAB mice in response to hypoxia (*p < .05). C) Summary of MAPD90 shortening (left), half-time (t1/2) of MAPD90 shortening (middle), and rate of MAPD90 shortening (right) in hearts from sham and TAB mice in response to heart rate acceleration (*p < .05).
Fig 6.
Protective effects of CaMKII inhibition on cardiac ischemia-reperfusion injury is mediated through KATP channels.
A) Representative tetrazolium chloride (TTC) staining of fresh ventricular sections after ischemia-reperfusion injury in 4 groups: wild-type (WT), transgenic mice with cardiac-specific expression of a CaMKII inhibitor (AC3-I), mice with knock out of the cardiac KATP channel pore-forming subunit, Kir6.2 in combined with transgenic cardiac expression of a CaMKII inhibitor (AC3-I/Kir6.2 KO) and mice with knock out of Kir6.2 only (Kir6.2 KO). B) Summary of normalized myocardial infarction size expressed as the average % tissue area stained by TTC in multiple sections of ventricles in response to ischemia-reperfusion (*p < .05 vs. WT).