GLUTAMINE STABILITY IN BIOLOGICAL TISSUES EVALUATED BY FLUOROMETRIC ANALYSIS

Although glutamine has been considered unstable during storage and the refore difficult to quantitate, recent results suggest this amino acid is stable at low pH ranges. We evaluated the stability of glutamine i n plasma and tissue extracts, using fluorometric analysis. The measure d concentration of glutamine detected varied linearly up to 0.8 mmol/L for the aqueous solution (r2 = 98.7, P = 0.0001) with a mean (+/- SD) coefficient of variation of 2.41% +/- 0.79%. When glutamine was disso lved in 50 g/L trichloroacetic acid (TCA), the values were essentially unaltered. Glutamine in an aqueous solution and stored at -70-degrees -C was stable for at least 16 days; glutamine in TCA was stable for 6- 8 days, then decreased to a concentration significantly lower than tha t of the aqueous solution. The expected and observed concentrations in plasma were equal (r2 = 0.99975) for increasing amounts of added glut amine. Glutamine concentrations in plasma were stable for > 1 year whe n stored at -70-degrees-C. The glutamine of a transplantable rat sarco ma and a normal rat liver could be extracted with 50 g/L TCA with high efficiency (88.6% +/- 1.9% and 90.2% +/- 0.04%, respectively); the ex tracted glutamine is stable in TCA for at least 7 days without neutral ization when stored at -70-degrees-C. Fluorometric analysis of glutami ne required only a small quantity of plasma (25 muL) or tissue (200 mg ) and is a convenient method for quantifying this important amino acid .