Enzymatic Synthesis and Organ Distribution Studies with13N-Labeled L-Glutamine and L-Glutamic Acid

A method was developed for producing several hundred mCi of 13NH3 with subsequent enzymatic synthesis of large amounts of 13N-labeled glutamine and glutamic acid. Dynamic measurements and quantitative whole body scans demonstrated greater glutamine uptake in the liver region of mongrel dogs than uptake of glutamic acid or NH3, although all concentrated in the liver to a significant degree. Myocardial uptake of glutamine and glutamic acid was low, while NH3 was incorporated into the heart, brain, bladder, and kidneys at a greater rate than the amino acids.