Changes in metabolism and urinary excretion of antipyrine induced by aerobic conditioning

Background. Physical conditioning has been reported to increase liver oxida tive metabolism determined by antipyrine clearance. The purpose of this inv estigation was to study effects of aerobic conditioning on the different me tabolic pathways of antipyrine by comparing the production clearances of an tipyrine metabolites. Methods. Participant: volunteers not engaged in the systematic practice of any sport (n=14) were compared with aerobically-conditioned subjects (n=14) Gong distance runners, defined as men running >80 km/week). Interventions: antipyrine was administered orally. Saliva samples were collected under ba sal conditions and at 8, 16, 24, 32 and 40 hrs following antipyrine adminis tration. Urine was collected for 24 hrs after antipyrine ingestion. Measures: endurance performance was expressed by the maximal oxygen uptake ((V) over dot O(2)max), the ventilatory threshold and the 4 mM.l(-1) lactat e threshold (OBLA). Antipyrine pharmacokinetic parameters (antipyrine clear ance and half-live) were obtained from saliva samples by the standard multi ple-sample method. Results. (V) over dot O(2)max, ventilatory threshold and OBLA were higher i n trained than in control subjects (+32 %, +16% and +74%, respectively). Sa livary antipyrine clearance was higher, whether or not this variable was co rrected for weight (+26% and +38%, respectively), and antipyrine half-life was significantly reduced (-31%) in runners. There was no significant chang e with training in the renal clearance of antipyrine or in the norantipyrin e (NORA) formation clearance but significant increases were observed in hyd roxymethylantipyrine (HMA) and 4-hydroxyantipyrine (OHA) formation clearanc es (+42 and +37%, respectively). Conclusions. The findings indicate that aerobic conditioning leads to incre ased disposition of antipyrine and that the main metabolic pathways of the compound are changed differently.