title: Effect of amino acid infusion on central thermoregulatory control in humans.
abstract: BACKGROUND
  Administration of protein or amino acids enhances thermogenesis, presumably by stimulating oxidative metabolism. However, hyperthermia results even when thermoregulatory responses are intact, suggesting that amino acids also alter central thermoregulatory control. Therefore, the authors tested the hypothesis that amino acid infusion increases the thermoregulatory set point.
  
  
  METHODS
  Nine male volunteers each participated on 4 study days in randomized order: (1) intravenous amino acids infused at 4 kJ x kg(-1) x h(-1) for 2.5 h combined with skin-surface warming, (2) amino acid infusion combined with cutaneous cooling, (3) saline infusion combined with skin-surface warming, and (4) saline infusion combined with cutaneous cooling.
  
  
  RESULTS
  Amino acid infusion increased resting core temperature by 0.3 +/- 0.1 degrees C (mean +/- SD) and oxygen consumption by 18 +/- 12%. Furthermore, amino acid infusion increased the calculated core temperature threshold (triggering core temperature at a designated mean skin temperature of 34 degrees C) for active cutaneous vasodilation by 0.3 +/- 0.3 degrees C, for sweating by 0.2 +/- 0.2 degrees C, for thermoregulatory vasoconstriction by 0.3 +/- 0.3 degrees C, and for thermogenesis by 0.4 +/- 0.5 degrees C. Amino acid infusion did not alter the incremental response intensity (i.e., gain) of thermoregulatory defenses.
  
  
  CONCLUSIONS
  Amino acid infusion increased the metabolic rate and the resting core temperature. However, amino acids also produced a synchronous increase in all major autonomic thermoregulatory defense thresholds; the increase in core temperature was identical to the set point increase, even in a cold environment with amble potential to dissipate heat. In subjects with intact thermoregulatory defenses, amino acid-induced hyperthermia seems to result from an increased set point rather than increased metabolic rate per se.
authors.affiliation: Department of Anesthesiology, Kyoto Prefectural University of Medicine, Kyoto, Japan. nakajima@koto.kpu-m.ac.jp
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Akira
authors.initials: A
authors.lastname: Takamata
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsukawa
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kitamura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ueno
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Toshiki
authors.initials: T
authors.lastname: Mizobe
mesh_terms: D000328:Adult; D000465:Algorithms; D000596:Amino Acids / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects*; D004837:Epinephrine / Q000097:blood; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects; D012039:Regional Blood Flow / Q000187:drug effects; D012867:Skin / Q000098:blood supply; D013546:Sweating / Q000187:drug effects
chemical_list: D000596:Amino Acids; D009638:Norepinephrine; D004837:Epinephrine