Few studies examine ammonia and amino acid metabolism in response to endurance training. Trained humans generally experience less increase in plasma ammonia during either prolonged or intense exercise. This is probably a reflection of reduced ammonia production and release from the active muscle; it could be a reflection of decreased AMP deaminase activity, decreased glutamate dehydrogenase activity, and/or increased alanine and glutamine formation. Little is known regarding the associated enzyme systems in humans, but in experiments with animal models, aerobic training decreases AMP deaminase and increases the enzymes of amino acid transmination and oxidation.
Copenhagen Muscle Research Centre, August Krogh Institute, University of Copenhagen, 2100 Copenhagen O, DENMARK
Submitted for publication January 1996.
Accepted for publication March 1996.
The work of T. Graham has been supported by NSERC of Canada. The collaborative research among the authors has been supported by the Copenhagen Muscle Research Centre, as well as the Medical Research Council, the Natural Sciences Research Council, and the Sport Research Council of Denmark.
Current address for L. Turcotte: Department of Exercise Science, University of Southern California, PED 107, University Park, CA 90089-0652.
Address for correspondence: T. Graham, School of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.