Determination of plasma [6,6-²H₂]glucose enrichment by a simple and accurate gas chromatographic-mass spectrometric method

An improved method for the evaluation of glucose turnover rate in humans, using a prime-continuous infusion of [6,6-²H₂]glucose, was developed. Deproteinization of plasma and conversion of glucose into the aldononitrile pentaacetate derivative are the only sample manipulations required prior to the gas chromatographic-mass spectrometric analysis. In six normal adults (prime = 5 mg kg^-1; continuous infusion = 0.05 mg kg^-1 min^-1) the hepatic glucose output calculated at steady state by the procedure described here was 2.1 ± 0.2 mg kg^-1 min^-1, the isotopic enrichment being determined with a coefficient of variation of ca. 2%. In six additional subjects, with half of the above-mentioned doses of labelled glucose, the mean hepatic glucose output was exactly the same (3.2% coefficient of variation for the isotopic enrichment measurement). The method described allows the hepatic glucose output to be precisely determined with savings both of time and of labelled glucose.