Chylomicron metabolism by the isolated perfused mouse heart.
The catabolism of rat chylomicrons, labeled in their triacylglycerol (TG) component, was investigated using perfused working mouse hearts. Perfusion of mouse hearts with heparin increased lipoprotein lipase (LPL) activity in the perfusate. This heparin-releasable LPL pool remained constant over a variety of experimental conditions, including workload and fatty acid concentrations, making the mouse heart a suitable model to study chylomicron catabolism. Endothelium-bound LPL hydrolyzed radiolabeled (3)H-labeled chylomicrons (0.4 mM TG); the fate of LPL-derived (3)H-labeled fatty acids was split evenly between oxidation (production of (3)H(2)O) and esterification (incorporation into tissue lipids, mainly TG). In comparison, the oxidation of 0.4 mM [(3)H]palmitate complexed to albumin was fourfold greater than esterification into tissue lipids. Surprisingly, the addition of unlabeled palmitate (0.4 or 1.2 mM) to perfusions with (3)H-chylomicrons did not affect the fate (either oxidation or esterification) of LPL-derived (3)H-fatty acids. These results suggest that fatty acids produced from lipoprotein hydrolysis by the action of LPL and fatty acids from a fatty acid-albumin complex do not enter a common metabolic pool in the heart.
Mardy
K
K
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
Belke
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Severson
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D000818:Animals; D002914:Chylomicrons / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004951:Esterification / Q000187:drug effects; D006321:Heart / Q000187:drug effects; D006493:Heparin / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D008071:Lipoprotein Lipase / Q000378:metabolism; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D019308:Palmitic Acid / Q000378:metabolism / Q000494:pharmacology; D010477:Perfusion; D051381:Rats; D012709:Serum Albumin / Q000378:metabolism; D014316:Tritium
D002914:Chylomicrons; D046911:Macromolecular Substances; D012709:Serum Albumin; D014316:Tritium; D019308:Palmitic Acid; D006493:Heparin; D008071:Lipoprotein Lipase