title: Model systems for modulating the free energy of ATP hydrolysis in normoxically perfused rat hearts.
abstract: This study has two objectives; first, to develop perfusion conditions that decrease the free energy of ATP hydrolysis, Delta GATP, in isolated hearts; and, second, to modulate the Delta GATP in these perfused hear models. To accomplish the first goal, a series of inhibitors was employed to restrict acetyl-CoA oxidation. The second goal was accomplished by increasing work demand. Rat hearts were perfused with Krebs-Henseleit solution containing glucose and either; (i) no inhibitors (G group hearts); (ii) 0.3 mm bromo-octanoate (BrO), an inhibitor of beta-oxidation (GB group); (iii) 0.4 mm amino-oxyacetate (AOA), an inhibitor of the malate-aspartate shuttle (GA group); (iv) BrO and AOA (GBA group hearts); or (v) BrO, AOA, and 4 mm butyrate, an alternate substrate (GBA-Bu). Pacing hearts at 300 beats per min (beats/min), at 450 beats/min, and at 450 beats/min in the presence of 80 microgram/l dobutamine allowed three increasing levels of work demand to be attained. The Delta GATP values of the five groups of hearts were calculated for each workstate using the concentrations of high energy phosphate metabolites measured by 31P NMR spectroscopy. At the highest levels of workload demand, the G, GB, and GBA-Bu group hearts had Delta GATP values >/=-53 kJ/mol ATP. At the highest levels of workload demand, the GA and GBA hearts had Delta GATP values </=-49 kJ/mol ATP. The values of Delta GATP and the heart work output during any perfusion conditions were stable for periods of >20 min. The G, GB, and GBA-Bu hearts attained RPPs of >/=54x10(3) mmHg/min at the highest levels of workload demand. The GA and GBA hearts attained RPPs of </=30x10(3) mmHg/min at the highest levels of workload demand. This study establishes stable, non-ischemic, isolated perfused heart preparations with which Delta GATP can be easily varied across the physiological relevant range of -56 to -47 kJ/mol ATP.
authors.affiliation: Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, AL, 35294-4470, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Balschi
authors.forename: H
authors.initials: H
authors.lastname: Shen
authors.forename: M C
authors.initials: MC
authors.lastname: Madden
authors.forename: J O
authors.initials: JO
authors.lastname: Hai
authors.forename: E L
authors.initials: EL
authors.lastname: Bradley
authors.forename: P E
authors.initials: PE
authors.lastname: Wolkowicz
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000332:Aerobiosis; D000818:Animals; D006868:Hydrolysis; D066298:In Vitro Techniques; D007773:Lactates / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008955:Models, Cardiovascular; D009206:Myocardium / Q000378:metabolism*; D010084:Oxidation-Reduction; D010477:Perfusion; D010758:Phosphorus; D051381:Rats; D017207:Rats, Sprague-Dawley; D013816:Thermodynamics
chemical_list: D007773:Lactates; D010758:Phosphorus; D000255:Adenosine Triphosphate