Analysis of sequential events in intestinal absorption of folylpolyglutamate
Although it is clear that the intestinal absorption of folylpolyglutamates is associated with hydrolysis to monoglutamyl folate, the precise sequence and relative velocity of the events involved in this absorption are not fully elucidated. In the present study, we used biosynthetic, radiolabeled folylpolyglutamates purified by affinity chromatography to analyze the relationship of hydrolysis and transport in rat jejunal loops in vivo. Absorption was best described by a series of first-order processes: luminal hydrolysis to monoglutamyl folate followed by tissue uptake of the product. The rate of hydrolysis in vivo was twice as high as the rate of transport. The latter value was identical to that measured for folic acid administered separately. The relevance of this sequential model was confirmed by data obtained using inhibitors of the individual steps in absorption of ''natural'' folate. Heparin and sulfasalazine were both effective in decreasing absorption. The former affected hydrolysis solely, whereas the latter acted as a competitive inhibitor of transport of monoglutamyl folate. These studies confirm that hydrolysis is obligatory and that the product is subsequently taken up by a transport process, common to monoglutamyl folates, that is the rate-determining step in transepithelial absorption.
- Research Organization:
- Univ. of Chicago, IL (USA)
- OSTI ID:
- 7095335
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 255
- Country of Publication:
- United States
- Language:
- English
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GLUTAMIC ACID
INTESTINAL ABSORPTION
CHROMATOGRAPHY
FOLIC ACID
HEPARIN
HYDROLYSIS
IN VIVO
MEMBRANE TRANSPORT
METABOLISM
RATS
SMALL INTESTINE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ABSORPTION
AMINES
AMINO ACIDS
ANIMALS
ANTICOAGULANTS
AROMATICS
AZAARENES
BODY
CARBOHYDRATES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECOMPOSITION
DIGESTIVE SYSTEM
DRUGS
GASTROINTESTINAL TRACT
HEMATINICS
HEMATOLOGIC AGENTS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INTESTINES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LYSIS
MAMMALS
MUCOPOLYSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
POLYSACCHARIDES
PTERIDINES
RODENTS
SACCHARIDES
SEPARATION PROCESSES
SOLVOLYSIS
UPTAKE
VERTEBRATES
VITAMIN B GROUP
VITAMINS
550501* - Metabolism- Tracer Techniques