Short-term metabolic fate of 13N-labeled glutamate, alanine, and glutamine(amide) in rat liver.

摘要: Tracer quantities (in 0.2 ml) of 13N-labeled glutamate, alanine, or glutamine(amide) were administered rapidly (less than equal to 2 s) via the portal vein anesthetized adult male rats. Liver content tracer at 5 s was 57 +/- 6 (n = 6), 24 1 3), and 69 7 3)% injected dose, respectively. Portal-hepatic differences for corresponding amino acids 17 6, 26 8, 19 9% 4), respectively, suggesting some export glutamate glutamine, but not hepatic vein. Following L-[13N]glutamate administration, label appeared in liver alanine aspartate (within seconds). The data emphasize rapidity nitrogen exchange linked transaminases. By 30 following administration either L-[13N]alanine, comparable; yet, by min greater 9 times as much present glutamine(amine) L-[13N]alanine administration. Conversely, urea more pronounced latter case despite: (a) comparable total pool sizes liver; (b) incorporation from into must occur prior transfer glutamate. provide evidence zonal uptake vivo. rate turnover L-[amide-13N]glutamine considerably slower that L-[13N]glutamate, presumably due part higher concentration glutamine organ. Nevertheless, it possible show despite occasional suggestions contrary, is a source findings continue reactions