Glycogen depletion as indication for ammonia determination in exercise testing

Abstract

During intensive exercise, ammonia is formed in skeletal muscle by deamination of AMP. In this way, plasma ammonia (Am) can be regarded as an indicator of the dephosphorylation state in the working muscle. In case of glycogen depletion, the behavioral patterns of lactate and ammonia are qualitatively different. Whereas lactate decreases at the same workload, ammonia increases significantly. Therefore, the determination of Am is interesting in exercise testing as it may help to differentiate between an endurance training effect and glycogen depletion. If ammonia concentrations are obtained from different performance exercise tests, the influence of the test protocol (velocity of workload increase, time interval for blood sampling) and exercise mode on the behavior of plasma ammonia has to be considered. Furthermore, women show significantly lower submaximal and maximal plasma ammonia concentrations compared with men. Methodical sources of error, which cause high intra-individual variation of plasma ammonia such as pollution of environment, glassware, staff, and subjects with ammonia and in-vitro accumulation of plasma ammonia because of hemolysis, sweat, blood clotting, and temperature, have to be avoided by the laboratory staff.

Keywords:

• ammonia
• purine nucleotides
• lactate
• energy metabolism
• exercisetesting
• glycogen depletion