DIFFERENTIAL INCORPORATION OF C-13 LABEL FROM DIETARY GLUCOSE INTO NEUTRAL SUGARS OF RAT INTESTINE MACROMOLECULES

Using gas chromatography-isotope ratio mass spectrometry, the detectio n, with a good reproducibility and in a single step, of the C-13 conte nt of glycoprotein neutral sugars, glycogen glucose, and ribonucleic a cid ribose allowed us to trace incorporation into intestinal macromole cules of sugars derived from dietary glucose, labeled either naturally (as corn starch) or artificially. The C-13 enrichment of glycoprotein neutral sugars was strong and rapid and plateaued up to the end of th e experiment, whereas the C-13 content of ribose increased linearly wi th time. By contrast, with artificially enriched dietary glucose, no s ignificant C-13 enrichment was detected in glycogen, suggesting that t his macromolecule does not directly derive from dietary glucose. These results suggest differential control of sugars involved in the synthe sis of intestinal macromolecules and demonstrate that this technique w ould be sensitive and reliable enough to be applied in man for serum g lycoprotein sugar determinations.