title: Effect of epinephrine on net lactate uptake by contracting skeletal muscle.
abstract: The purpose of this study was to determine the effect of epinephrine on net lactate (La(-)) uptake at constant elevated blood La(-) concentration and steady level metabolic rate (O(2) uptake) in the canine gastrocnemius-plantaris muscle in situ. Infusion of La(-)/lactic acid (pH 3.5) established a mean arterial blood La(-) concentration of ~10 mM while normal blood-gas and pH status were maintained as the gastrocnemius-plantaris was stimulated with tetanic trains at a rate of one contraction every 4 s. After steady-state control measures, epinephrine was infused for 35 min at rates that produced a high physiological concentration with (Pro; n = 6) and without (Epi; n = 6) beta-adrenergic-receptor blockade via propranolol. Net La(-) uptake values during the control conditions were not significantly different between trials (Epi: 0.756 +/- 0.043; Pro: 0.703 +/- 0.061 mmol. kg(-1). min(-1)). Steady level O(2) uptake averaged approximately 69.5 ml. kg(-1). min(-1) for both control conditions and did not significantly change over the course of the experiments in either set of trials. Epi experiments resulted in a significantly reduced net La(-) uptake (0.346 +/- 0.088 mmol. kg(-1). min(-1) after 5 min of infusion) compared with control value at all sample times measured. However, net La(-) uptake was not significantly different from control at any time during Pro (0.609 +/- 0.052 mmol. kg(-1). min(-1) after 5 min of infusion). When the change from the respective control values for net La(-) uptake was compared across time for both series of experiments, Epi resulted in a significantly greater change from control than did Pro. This study suggests that epinephrine can have a profound effect on net La(-) uptake by contracting muscle and that these effects are elicited through beta-adrenergic-receptor stimulation.
authors.affiliation: Department of Health and Human Performance, Auburn University, Auburn, AL 36849, USA. hamannj@mcw.edu
authors.forename: J J
authors.initials: JJ
authors.lastname: Hamann
authors.forename: K M
authors.initials: KM
authors.lastname: Kelley
authors.forename: L B
authors.initials: LB
authors.lastname: Gladden
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D006706:Homeostasis; D019344:Lactic Acid / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D010101:Oxygen Consumption; D011433:Propranolol / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D019344:Lactic Acid; D011433:Propranolol; D004837:Epinephrine