1. Turnover parameters for plasma glycine were measured by administration of a single dose of [15N]glycine to overnight fasted healthy volunteers, nine patients with chronic leukaemia, one patient with acute monocytic leukaemia and one patient with chronic myeloid leukaemia before and after chemotherapy.
2. Gas chromatography-mass spectrometry was used to determine plasma [15N]glycine enrichment. Pool sizes and turnover rate constants were estimated from time-decay curves for isotope enrichment.
3. Turnover rate constants and metabolic clearance rates of plasma glycine in leukaemia patients were elevated in comparison with data for healthy volunteers. The increased rates of glycine disappearance from the circulation were not accompanied by a depletion in glycine pool size. Turnover rate constants fell during chemotherapy and were within the normal range during remission.
4. There was a significant positive correlation between glycine turnover rate constants and leucocyte counts.
5. The increase in glycine turnover rate constants may be related to proliferation of the neoplastic cells.