The distribution and turnover of 35S methionine as influenced by diet in the dark-eyed Junco (Junco hyemalis)

1. Dark-eyed Juncos (Junco hyemalis) were maintained on one of three semi-synthetic diets, differing only in their sulphur amino acid content. 2. 35S-methionine was administered intraperitoneally after 3 days on their respective diets and the animals were killed 24 or 96 hr post-injection. 3. Faecal loss of 35S-methionine was significantly lower in the low methionine/high cysteine (HC) group after 24 hr when compared with other two dietary groups (4.69 vs 5.53 and 5.47%) indicating a whole-body conservation of the limiting amino acid. 4. Incorporation of 35S-methionine in hepatic and intestinal tissues was also greater in the HC group, even as the animals were losing body weight.