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

Physical conditioning has been reported to increase liver oxidative metabolism determined by antipyrine clearance. The purpose of this investigation was to study effects of aerobic conditioning on the different metabolic pathways of antipyrine by comparing the production clearances of antipyrine metabolites.

volunteers not engaged in the systematic practice of any sport (n = 14) were compared with aerobically-conditioned subjects (n = 14) (long distance runners, defined as men running > 80 km/week).

antipyrine was administered orally. Saliva samples were collected under basal conditions and at 8, 16, 24, 32 and 40 hrs following antipyrine administration. Urine was collected for 24 hrs after antipyrine ingestion.

endurance performance was expressed by the maximal oxygen uptake (VO2max), the ventilatory threshold and the 4 mM.l-1 lactate threshold (OBLA). Antipyrine pharmacokinetic parameters (antipyrine clearance and half-live) were obtained from saliva samples by the standard multiple-sample method.

VO2max, ventilatory threshold and OBLA were higher in trained than in control subjects (+32%, +16% and +74%, respectively). Salivary antipyrine clearance was higher, whether or not this variable was corrected for weight (+26% and +38%, respectively), and antipyrine half-life was significantly reduced (-31%) in runners. There was no significant change with training in the renal clearance of antipyrine or in the norantipyrine (NORA) formation clearance but significant increases were observed in hydroxymethylantipyrine (HMA) and 4-hydroxyantipyrine (OHA) formation clearances (+42 and +37%, respectively).

The findings indicate that aerobic conditioning leads to increased disposition of antipyrine and that the main metabolic pathways of the compound are changed differently.