GLUCOSE AND GLUTAMINE PROVIDE SIMILAR PROPORTIONS OF ENERGY TO MUCOSAL CELLS OF RAT SMALL-INTESTINE

The objectives of this study were to establish a reliable method for q uantifying glycolytic flux in intestinal epithelial cells, to determin e the proportion of energy provided to small intestine epithelial cell s by glucose vs. glutamine, and to determine whether there was an ener getic advantage to having both substrates present simultaneously. Ther e was substantial retention of H-3 in alanine and lactate when [2-H-3] glucose was used as tracer for quantifying glycolysis, and the magnitu de of the H-3 retention was influenced by the presence of other substr ates and metabolites. Detritiation was at least 99% complete, however, when [3-H-3]glucose was used as tracer in this system and the tritium was recovered as (H2O)-H-3. Glycolytic flux was six-to sevenfold high er in cells of the proximal than distal small intestine but was not si gnificantly different for young adult (4 mo) vs. aged adult (24 mo) ra ts. Net ATP production from exogenous substrates was higher when both glucose and glutamine were present simultaneously than when either sub strate was present alone, and glucose was calculated to provide 50-60% of the net ATP produced from these two substrates. Most of the energy produced from glucose was produced via the anaerobic metabolic pathwa ys (78% for glucose alone, 95% with glucose and glutamine). Net energy production was calculated to be 10% lower in cells from aged animals than in those from young animals, since CO2 production from these majo r substrates was lower in cells from aged animals.