[Studies on the 14C-15N-acetamide turnover in sheep. 1. Studies on the 14C turnover]

4 male sheep (average weight: 53.5 kgs) were fed a semisynthetic diet containing acetamide as sole source of nitrogen. At the beginning of the trial twin-labelled 15N-14C-acetamide was administered by way of a ruminal fistula. The curve pattern of 14C activity in the TCE-soluble fraction of the ruminal fluid showed a synchronous behaviour in all animals beginning at 3 hours after the beginning of the trial. A half-life of 2 1/2 hours for the rate of absorption of 14C acetamide and deaminated 14C acetate was established from the decline in 14C activity observed in the TCE-soluble fraction of the ruminal fluid. The peak level of 14C labelling in ruminal proteins was reached after 6 hrs. The specific 14CO2 activity in respiratory air reached its maximum level after 4 hrs, and was then found to decline continuously. 56% of the administered amount of 14C was excreted over a period of up to 50 hrs after beginning of the trial. The very fact that the peak level of 14C activity was observed to appear in the TCE-soluble fraction of the blood plasma as early as after 1 hr seems to indicate that acetamide is also absorbed through the ruminal wall. The half-life of decline in the 14C activity of this fraction was 5.7 hrs. Analysis by thin layer chromatography showed that 75% of this amount of activity is present in 14C acetamide. The rate of 14C incorporation into blood plasma proteins reached a plateau region after 21 hrs, which was also maintained on the 2nd day of the experiment. 6.5% of the administered amount of 14C activity was excreted in the urine until the 7th day of experiment. 76.6% of the amount of urinary 14C activity excreted within a period of 48 hrs were voided as 14C acetamide. 3.8% of the administered amount of 14C activity was excreted with the faeces within the first 6 days of experiment.