Incorporation of intraportally infused [15N]ammonia into urinary uric acid in cockerels pretreated with methionine sulfoximine.

1. Measurements were made in situ to determine the incorporation of intraportally infused ammonia-15N into urinary uric acid in cockerels pre-treated with methionine sulfoximine (MSM), a glutamine synthetase inhibitor. 2. The incorporation of 15N into urinary uric acid was 34% of the infused amount in MSM-treated birds. This was not significantly different from the value of 46% for control birds. 3. Pre-treatment with MSM inhibited the activity of liver glutamine synthetase to 7% of the control value and decreased the incorporation of the infused ammonia-15N into plasma glutamine amide-N to 3% of the control. 4. Increases in glutamine concentrations in the blood, liver and kidney caused by the infusion of ammonia were also completely inhibited by the MSM treatment (P less than 0.05). 5. It is concluded that in the cockerel ammonia-N can be incorporated into uric acid other than by glutamine formation.