Substrate metabolism in isolated rat jejunal epithelium. Analysis using /sup 14/C-radioisotopes
The jejunal epithelium absorbs nutrients from the intestinal lumen and is therefore the initial site for metabolism of these compounds. The purpose of this investigation is to analyze substrate metabolism in a preparation of jejunal epithelium relatively free of other tissues. Novel radioisotopic labelling techniques allow quantitation of substrate metabolism in the TCA cycle, Embden-Meyerhof (glycolytic) pathway, and hexose monophosphate shunt. For example, ratios of /sup 14/CO/sub 2/ production from pairs of /sup 14/C-pyruvate, and /sup 14/C-succinate radioisotopes (CO/sub 2/ ratios) indicate the probability of TCA cycle intermediate efflux to generate compounds other than CO/sub 2/. With (2,3-/sup 14/C)succinate as tracer, the ratio of /sup 14/C in carbon 4 + 5 versus carbon 2 + 3 of citrate, the citrate labelling ratio, equals the probability of TCA intermediate flux to the acetyl CoA-derived portion of citrate versus flux to the oxaloacetate-derived portion. The principal metabolic substrates for the jejunal epithelium are glucose and glutamine. CO/sub 2/ ratios indicate that glutamine uptake and metabolism is partially Na/sup +/-independent, and is saturable, with a half-maximal rate at physiological plasma glutamine concentrations. Glucose metabolism in the jejunal epithelium proceeds almost entirely via the Embden-Meyerhof pathway. Conversion of substrates to multi-carbon products in this tissue allows partial conservation of reduced carbon for further utilization in other tissues. In summary, metabolic modeling based on /sup 14/C labelling ratios is a potentially valuable technique for analysis of metabolic flux patterns in cell preparations.
- Research Organization:
- George Washington Univ., Washington, DC (USA)
- OSTI ID:
- 6717639
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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CARBON 14 COMPOUNDS
METABOLISM
GLUCOSE
GLUTAMINE
SMALL INTESTINE
BIOLOGICAL PATHWAYS
CARBON DIOXIDE
EPITHELIUM
PHYSIOLOGY
PYRUVIC ACID
SUCCINIC ACID
ALDEHYDES
AMIDES
AMINO ACIDS
ANIMAL TISSUES
BODY
CARBOHYDRATES
CARBON COMPOUNDS
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
DICARBOXYLIC ACIDS
DIGESTIVE SYSTEM
GASTROINTESTINAL TRACT
HEXOSES
INTESTINES
KETO ACIDS
LABELLED COMPOUNDS
MONOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
OXIDES
OXYGEN COMPOUNDS
SACCHARIDES
TISSUES
551001* - Physiological Systems- Tracer Techniques