The effect of sex on antipyrine metabolism in cattle at different ages

The aim of this study was to determine the effect of sex on the metabolism of antipyrine by measuring the antipyrine plasma clearance as well as excre tion of three major metabolites in urine in cattle of different ages. The experiment was carried out on 10 female and 10 male cattle of Black and White breed. The antipyrine test was carried out at 1, 2, 4, 6, 8, 12 and 18 months of age for each animal (single dose of 10 mg/kg antipyrine were g iven intravenously). The concentrations of antipyrine, 4-hydroxyantipyrine (4-OHA), 3-hydroxymethylantipyrine (HMA) and norantipyrine (NORA) were meas ured in plasma and urine by high performance liquid chromatography (HPLC). The apparent volume of distribution of antipyrine (aV(d)) decreased signifi cantly between 1 and 18 months of age, but mean aV(d) values observed in ma les and females were not statistically different. The experimental period w as characterised by a steady decrease (statistically significant) in antipy rine half-life (t(1/2 beta)), These values did not differ significantly bet ween males and females under 12 months. In 12 and 18 month-old animals the antipyrine half-life in the females was significantly shorter than in the m ales. The systemic clearance (Cl-s) of antipyrine increased significantly b etween 1 and 18 months of age. No significant differences were observed bet ween systemic clearance of antipyrine in males and females under 12 months. In 12 and 18 month-old animals the Cl-s values were significantly higher i n females than in males. Following intravenous administration, recovery of antipyrine and its three main metabolites increased significantly with age. These values did not differ significantly between males and females under 12 month of age, In 12 and 18 month-old females the excretion of 4-OHA and HMA in urine was significantly higher than in males at the same age. The ex cretion of NORA and unchanged antipyrine in males and females did not diffe r significantly. The partial clearances of antipyrine metabolites (Cl-m) in creased significantly between 1 and 18 months of age. No significant differ ences were observed between Cl-m values in males and females under 12 month s of age. In 12 and 18 month-old females the partial clearances of 4-OHA an d HMA were significantly higher than in males. The clearance of NORA was si gnificantly higher in 18 month-old females than in males. In conclusion, we report a sex-linked difference in plasma antipyrine clear ance and urinary excretion of the main metabolites of antipyrine in cattle over 12 months of age, the females being the more active metabolizers.