Alanine kinetics in humans: influence of different isotopic tracers.
Whole-body alanine kinetics were studied using continuous infusions of [15N]-, [3,3,3-2H3]-, [1-13C]-, and [3-13C]alanine tracers in healthy male subjects in the postabsorptive state. Alanine kinetics were highly dependent on the choice of isotopically labeled alanine. Highest rates of alanine flux (mean +/- SE) were obtained with the [3,3,3-2H3]alanine (474 +/- 41 mumol X kg-1 X h-1). [1-13C]- and [3-13C]alanine tracers gave intermediate values (297 +/- 12 and 317 +/- 22 mumol X kg-1 X h-1, respectively). The slowest rates of alanine turnover were measured with [15N]alanine (226 +/- 7 mumol X kg-1 X h-1). These results emphasize the heterogeneous metabolism of different portions of the alanine molecule and the importance of choosing an appropriate alanine tracer for studying different aspects of alanine metabolism.
D000328:Adult; D000409:Alanine / Q000378:metabolism*; D001827:Body Height; D001835:Body Weight; D002247:Carbon Isotopes; D003903:Deuterium; D004032:Diet; D006801:Humans; D007700:Kinetics; D008297:Male; D009587:Nitrogen Isotopes
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D003903:Deuterium; D000409:Alanine