Determination of [14C] Glutamine Specific Activity in Plasma

Glutamine is a key amino acid participating in various metabolic pathways. Study of the physiology of its carbon skeleton has been hampered by lack of a simple and precise method to measure its [14C] specific activity in plasma. The present report describes an automated, sensitive and specific method to determine plasma [14C] glutamine specific activity which can be used to measure glutamine carbon turnover and substrate-product interactions in vivo. An orto-phtalaidehyde derivative is analysed on a reverse phase column by UV detection. With this procedure μMol amounts of glutamine and other plasma compounds can be assayed for [14C] specific activity. The method is sufficiently fast (25 samples in 24 hrs) and reproducible (CV<5.5%) for accurate measurements in a large volume of samples.