title: Ammonia metabolism during intense dynamic exercise and recovery in humans.
abstract: This study examined the dynamics for ammonia (NH3) metabolism in human skeletal muscle during and after intense one-legged exercise. Subjects (n = 8) performed dynamic leg extensor exercise to exhaustion (3.2 min). Muscle NH3 release increased rapidly to a maximum of 314 +/- 42 mumol/min and declined immediately on cessation of exercise. Recovery was complete in approximately 20 min. Arterial [NH3] increased less rapidly and reached its maximum 2-3 min into recovery. These data demonstrate that NH3 clearance is more sensitive to the cessation of exercise than is NH3 release from skeletal muscle. Muscle [NH3] increased three to fourfold during exercise and represented 74 +/- 8% of the total net NH3 formation. Thus the change in muscle [NH3] alone underestimates the NH3 production. There was no evidence that the muscle-to-venous blood NH3 ratio shifts in accordance with the H+ data. Thus other factors must contribute to the NH3 release from active muscle. The total net NH3 formed corresponded with the intramuscular inosine 5'-monophosphate accumulation, suggesting that the NH3 was derived from AMP deamination. Changes in the known modulators of AMP deaminase (ATP, ADP, H+) were moderate, so the mechanisms initiating the deamination remain obscure.
authors.affiliation: August Krogh Institute, Copenhagen, Denmark.
authors.forename: T E
authors.initials: TE
authors.lastname: Graham
authors.forename: J
authors.initials: J
authors.lastname: Bangsbo
authors.forename: P D
authors.initials: PD
authors.lastname: Gollnick
authors.forename: C
authors.initials: C
authors.lastname: Juel
authors.forename: B
authors.initials: B
authors.lastname: Saltin
mesh_terms: D000227:Adenine Nucleotides / Q000302:isolation & purification / Q000378:metabolism; D000328:Adult; D000641:Ammonia / Q000097:blood / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D015444:Exercise; D006801:Humans; D007291:Inosine Monophosphate / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010725:Phosphocreatine / Q000302:isolation & purification / Q000378:metabolism; D005082:Physical Exertion
chemical_list: D000227:Adenine Nucleotides; D010725:Phosphocreatine; D007291:Inosine Monophosphate; D000641:Ammonia