Muscle and whole body metabolism after norepinephrine.
The effect of an infusion of norepinephrine (0.42 nmol.kg-1.min-1) on energy metabolism in the whole body (using indirect calorimetry and the arteriovenous forearm catheterization techniques in eight healthy young male adults. The activity of the triglyceride-fatty acid cycle, which mainly operates in nonmuscular tissues, was also assessed by measuring glycerol turnover using [2H5]glycerol (to indicate lipolysis) and indirect calorimetry (to indicate net fat oxidation). Norepinephrine increased whole body oxygen consumption by almost 10% (P < 0.01), but the estimated oxygen consumption of muscles tended to decrease. Muscle blood flow (measured by 133Xe) and forearm blood flow (measured by strain-gauge plethysmography) were not significantly affected by norepinephrine, but the rate of uptake of nonesterified fatty acids and beta-hydroxybutyrate increased severalfold (P < 0.05), whereas that of glucose did not. The activity of the triglyceride-fatty acid cycle increased fourfold after norepinephrine administration, having a marginal effect on resting energy expenditure (approximately 1.5%) but accounting for approximately 15% of the increase in whole body energy expenditure. This study provides no evidence that skeletal muscle is an important site for norepinephrine-induced thermogenesis and suggests that an increase in the activity of the triglyceride-fatty acid cycle contributes to the norepinephrine-induced increase in energy expenditure of nonmuscular tissues.
Rowett Research Institute, Bucksburn, Aberdeen, Scotland.
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D000328:Adult; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects*; D004734:Energy Metabolism / Q000187:drug effects*; D005227:Fatty Acids / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005542:Forearm / Q000098:blood supply; D005990:Glycerol / Q000097:blood; D006801:Humans; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood / Q000494:pharmacology*; D012039:Regional Blood Flow; D012881:Skin Temperature / Q000187:drug effects
D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D005990:Glycerol; D009638:Norepinephrine