Jejunal epithelial glucose metabolism: effects of Na+ replacement.
The objective of this study was to characterize the effects of replacement of extracellular Na+ with a nontransportable cation, N-methyl-D-glucamine (NMDG+) on jejunal epithelial glucose metabolism. Jejunal epithelium isolated from male Sprague-Dawley rats was incubated in media containing 5 mM glucose, 0.5 mM glutamine, 0.5 mM beta-hydroxybutyrate, and 0.3 mM acetoacetate as the principal carbon sources. O2 consumption and total glucose utilization were reduced 30 and 50%, respectively, when Na+ was replaced with NMDG+. In both media, approximately 75% of utilized glucose carbon was converted to lactate. The rate of glucose metabolism via the hexose monophosphate shunt, as evaluated using specific 14CO2 yields from [1-14C]glucose and [6-14C]glucose, was not appreciably altered by Na+ replacement. Tricarboxylic acid (TCA) cycle flux was evaluated using 14CO2 production from [14C]glucose and [14C]pyruvate radioisotopes. Approximately 50% of TCA cycle flux was shunted into products other than CO2 in both media. The majority of the acetyl-CoA oxidized in the TCA cycle was derived from cytosolic pyruvate. It is concluded that removal of Na+ from the bathing medium substantially reduced glucose utilization via the Embden-Meyerhof pathway and TCA cycle in the jejunal epithelium.
D000818:Animals; D002952:Citric Acid Cycle / Q000187:drug effects; D004848:Epithelium / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis / Q000187:drug effects; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008536:Meglumine / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D010427:Pentose Phosphate Pathway / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000502:physiology*
D008536:Meglumine; D012964:Sodium; D005947:Glucose