Metabolism of D-[1,2-C-13]glucose and alpha-D-[1,2-C-13]glucose pentaacetate in tumoral pancreatic islet cells

Tumoral pancreatic islet cells of the RINm5F line were incubated, in groups of 25x10(6) cells each, for 120 min at 37 degrees C in media (5.0 ml) cont aining either alpha-D-[1,2-C-13]glucose pentaacetate (1.7 mM) or both D-[l, 2-C-13]glucose (1.7 mM) and acetate (8.5 mM). In both cases, the amounts of C-13-enriched metabolites (D-glucose, L-lactate and acetate) and non-enric hed metabolites (acetate) recovered in the incubation medium after incubati on were close to the initial amount of esterified or non-esterified D-[1,2- C-13]glucose and acetate, respectively. The C-13-enriched metabolites corre sponded mainly to double-labelled D-[1,2-C-13]glucose, L-[2,3-C-13]lactate and [1,2-C-13]acetate. The output of L-[2,3-C-13]lactate and [1,2-C-13]acet ate was about 3-4 times lower in the cells exposed to alpha-D-[l,2-C-13]glu cose pentaacetate than in those incubated with unesterified D-[1,2-C-13]glu cose. These findings indicate that, despite extensive hydrolysis of alpha-D -[1,2-C-13]glucose pentaacetate in the RINm5F cells, the hexose moiety of t he ester is less efficiently metabolized than unesterified D-[1,2-C-13]gluc ose tested at the same molar concentration (1.7 mM) in the presence of 8.5 mM acetate. Thus, a higher utilization of the hexose moiety of alpha-D-gluc ose pentaacetate than that of unesterified D-glucose, as previously documen ted in isolated pancreatic islets, represents a far-from-universal situatio n.