Alanine kinetics in humans: influence of different isotopic tracers
Yang, R.D.; Matthews, D.E.; Bier, D.M.; Lo, C.; Young, V.R.
American Journal of Physiology 247(5 Pt 1): E634-E638
1984
ISSN/ISBN: 0002-9513 PMID: 6496733 Document Number: 239657
Whole-body alanine [ALA] kinetics were studied using continuous infusions of [15N]-, [3,3,3-2H3]-, [1-13C]- and [3-13C]ALA tracers in healthy male subjects in the postabsorptive state. ALA kinetics were highly dependent on the choice of isotopically labeled ALA. Highest rates of ALA flux (mean .+-. SE) were obtained with the [3,3,3-2H3]ALA (474 .+-. 41 .mu.mol .cntdot. kg-1 .cntdot. h-1). [1-13C]- and [3-13C]ALA tracers gave intermediate values (297 .+-. 12 and 317 .+-. 22 .mu.mol .cntdot. kg-1 .cntdot. h-1, respectively). The slowest rates of ALA turnover were measured with [15N]ALA (226 .+-. 7 .mu.mol .cntdot. kg-1 .cntdot. h-1). These results emphasize the heterogeneous metabolism of different portions of the ALA molecule and the importance of choosing an appropriate ALA tracer for studying different aspects of ALA metabolism.