HYPERAMMONEMIA IN RELATION TO HIGH-INTENSITY EXERCISE DURATION IN MAN

Adenine nucleotide (AN) degradation has been shown to occur during int ense exercise in man and in the horse, at or close to the point of fat igue. The aim of the study was to compare plasma ammonia concentration ([NH3]) as a result of intense exercise with plasma [lactate]. Plasma glutamine concentration ([Gln]) was also measured pre- and post-exerc ise. On separate occasions, nine healthy subjects (two females) exerci sed on a motorised treadmill for periods of between 30 s and 210 s, at 5.6 m.s(-1) (0% incline). On one occasion, running at the same speed, two subjects ran at + 4% incline whilst one other subject ran at + 7% incline. Blood samples were taken and plasma was analysed for [lactat e], [NH3] and [Gin]. Subjects showed varying degrees of AN degradation as indicated by plasma [NH3]. A comparison of plasma [NH3] with that of plasma [lactate] indicated a marked increase in AN degradation, cor responding to a [lactate] of around 14 mmol.l(-1) in plasma. The data further support the hypothesis that there is a critical intramuscular pH below which there is a stimulus to AN degradation during intense ex ercise, possibly as a result of a substantial reduction in the kinetic s of adenosine diphosphate (ADP) rephosphorylation provided by phospho creatine, resulting in an increase in [ADP].