TY - JOUR
T1 - The energetic state within hibernating myocardium is normal during dobutamine despite inhibition of ATP-dependent potassium channel opening with glibenclamide
AU - McFalls, Edward O.
AU - Kelly, Rosemary F.
AU - Hu, Qingsong
AU - Mansoor, Abdul
AU - Lee, Joseph
AU - Kuskowski, Michael
AU - Sikora, Joseph
AU - Ward, Herbert B.
AU - Zhang, Jianyi
PY - 2007/11
Y1 - 2007/11
N2 - Within hibernating myocardium, it is uncertain whether a normal energetic state is present at baseline and whether maintaining that energy state during a catecholamine challenge is dependent on ATP-dependent potassium channel opening. In this study, 16 swine underwent a thoracotomy with placement of an external constrictor on the left anterior descending coronary artery (LAD) (hibernation model). Seven additional swine underwent a sham operation. At 10 wk, the myocardial energetic state in the LAD region was assessed by 31P-NMR spectroscopy, and the ratio of phosphocreatine to ATP (PCr/ATP) was determined at baseline, during glibenclamide treatment (0.5 mg/kg bolus with 50 μg/min iv), and during addition of dobutamine (40 μg·kg -1·min-1 iv). At baseline, transmural blood flow in the LAD and remote region was 0.75 ± 0.11 and 0.88 ± 0.09 ml·min-1·g-1, respectively (P < 0.01), in hibernating hearts and 0.83 ± 0.12 and 0.88 ± 0.15 ml·min-1·g-1, respectively (not significant), in sham-operated hearts. Under basal conditions, PCr/ATP in the LAD region of hibernating and sham pigs was 2.15 ± 0.04 and 2.11 ± 0.05, respectively (not significant). In sham pigs, addition of dobutamine to glibenclamide increased the double product from 10.4 ± 0.8 to 23.9 ± 4.0 mmHg·beats·min-1 × 1,000 (P < 0.05) and decreased transmural PCr/ATP from 2.06 ± 0.06 to 1.69 ± 0.06 (P < 0.05). Dobutamine increased the double product in hibernating pigs in a similar fashion and, despite a 40% lower blood flow response, induced an equivalent decrease in PCr/ATP from 2.04 ± 0.04 to 1.73 ± 0.08 (P < 0.05). In conclusion, we found that, in chronic hibernating swine myocardium with reduced basal blood flow and perfusion reserve, the transmural energetic state, defined by PCr/ATP, is normal during addition of dobutamine, despite inhibition of ATP-dependent potassium channel opening with glibenclamide. These data suggest that important adaptations other than the ATP-dependent potassium channel opening allow hibernating myocardium to operate over a lower range of the oxygen supply-demand relationship to protect against myocardial ischemia.
AB - Within hibernating myocardium, it is uncertain whether a normal energetic state is present at baseline and whether maintaining that energy state during a catecholamine challenge is dependent on ATP-dependent potassium channel opening. In this study, 16 swine underwent a thoracotomy with placement of an external constrictor on the left anterior descending coronary artery (LAD) (hibernation model). Seven additional swine underwent a sham operation. At 10 wk, the myocardial energetic state in the LAD region was assessed by 31P-NMR spectroscopy, and the ratio of phosphocreatine to ATP (PCr/ATP) was determined at baseline, during glibenclamide treatment (0.5 mg/kg bolus with 50 μg/min iv), and during addition of dobutamine (40 μg·kg -1·min-1 iv). At baseline, transmural blood flow in the LAD and remote region was 0.75 ± 0.11 and 0.88 ± 0.09 ml·min-1·g-1, respectively (P < 0.01), in hibernating hearts and 0.83 ± 0.12 and 0.88 ± 0.15 ml·min-1·g-1, respectively (not significant), in sham-operated hearts. Under basal conditions, PCr/ATP in the LAD region of hibernating and sham pigs was 2.15 ± 0.04 and 2.11 ± 0.05, respectively (not significant). In sham pigs, addition of dobutamine to glibenclamide increased the double product from 10.4 ± 0.8 to 23.9 ± 4.0 mmHg·beats·min-1 × 1,000 (P < 0.05) and decreased transmural PCr/ATP from 2.06 ± 0.06 to 1.69 ± 0.06 (P < 0.05). Dobutamine increased the double product in hibernating pigs in a similar fashion and, despite a 40% lower blood flow response, induced an equivalent decrease in PCr/ATP from 2.04 ± 0.04 to 1.73 ± 0.08 (P < 0.05). In conclusion, we found that, in chronic hibernating swine myocardium with reduced basal blood flow and perfusion reserve, the transmural energetic state, defined by PCr/ATP, is normal during addition of dobutamine, despite inhibition of ATP-dependent potassium channel opening with glibenclamide. These data suggest that important adaptations other than the ATP-dependent potassium channel opening allow hibernating myocardium to operate over a lower range of the oxygen supply-demand relationship to protect against myocardial ischemia.
KW - Hibernation
KW - High-energy phosphates
KW - Mitochondrial adaptations
KW - Myocardial ischemia
KW - Preconditioning
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U2 - 10.1152/ajpheart.00012.2007
DO - 10.1152/ajpheart.00012.2007
M3 - Article
C2 - 17720774
AN - SCOPUS:36148932951
SN - 0363-6135
VL - 293
SP - H2945-H2951
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
IS - 5
ER -