EN
In the experiment carried out on 15 lowland black and white cows aged 2—3 years in the 4—5th month of lactation a possibility of measurement a biotransformative activity of the liver (activity of microsomal monooxygenase connected with cytochrome P-450; MMO-P-450) on the basis of antipyrine (phenazone) elimination rate from milk was examined. Antipyrine was applied intravenously at a dose of 15 mg/kg bw. Blood and milk samples were collected before 0 time and after 1, 2, 4, 6, 8, 12, 18 and 24 h after administration of the test solution. The values of antipyrine pharmacokinetic parameters (Co-initial concentration, V₄-volume of distribution, ∆'-coefficient of distribution, k-constant elimination rate, t₀.₅-half life, ClĄ-metabolic clearance) calculated on the basis of antipyrine concentrations changes in plasma and milk were very similar and the observed differences were not significant. The obtained data showed that in cows is possible to determine precisely the activity of enzymatic system MMO-P-450 and hence consequently the rate of liver biotransformation on the basis of antipyrine elimination rate from milk.