title: Energy provision from glycogen, glucose, and fatty acids on adrenergic stimulation of isolated working rat hearts.
abstract: We postulated that glycogen is a significant energy substrate compared with fatty acids and glucose in response to adrenergic stimulation of working rat hearts. Oxidation rates were determined at 1-min intervals by release of 3H2O from [9,10-(3)H]oleate (0.4 mM, 1% albumin) and 14CO2 from exogenous [U-14C]glucose (5 mM) or, by a pulse-chase method, from [14C]glycogen. We estimated the 14C enrichment of glycogen metabolized at each time point to determine true rates of glycogen use. Based on the pattern of glycogen enrichment over time, glycogenolysis did not exhibit a high degree of preference for newly synthesized glycogen. Epinephrine (1 microM) increased contractile performance 86% but did not stimulate oleate oxidation. The increased energy demand was supplied by carbohydrates, initially by a burst of glycogenolysis (contributing 35% to total ATP synthesis for 5 min) and followed by delayed increase in the use of exogenous glucose (eventually contributing 29% to ATP synthesis). On the basis of the release of 14CO2 and [14C]lactate specifically from glucose or glycogen, we found that a larger portion of glycogen was oxidized compared with exogenous glucose, augmenting the yield of ATP from glycogen. Thus the heart responds to an acute increase in energy demand by selective oxidation of glycogen.
authors.affiliation: Department of Internal Medicine, University of Texas-Houston Medical School 77030, USA.
authors.forename: G W
authors.initials: GW
authors.lastname: Goodwin
authors.forename: F
authors.initials: F
authors.lastname: Ahmad
authors.forename: T
authors.initials: T
authors.lastname: Doenst
authors.forename: H
authors.initials: H
authors.lastname: Taegtmeyer
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D018663:Adrenergic Agents / Q000494:pharmacology*; D000818:Animals; D004734:Energy Metabolism / Q000502:physiology*; D004837:Epinephrine / Q000494:pharmacology*; D005227:Fatty Acids / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D018663:Adrenergic Agents; D005227:Fatty Acids; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D006003:Glycogen; D005947:Glucose; D004837:Epinephrine