skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Role of sodium ion in transport of folic acid in the small intestine

Abstract

The effect of sodium on folate transport across the intestinal luminal membrane was analyzed using two techniques: the influx chamber and isoalted brush-border membrane vesicles. Preincubation of tissue in Na -free medium did not have a consistent effect on folic acid influx provided that Na was present in the test solution. Replacement of Na in the test solution by choline resulted in a significant reduction of folic acid influx. However, when intestinal sheets that had been equilibrated in Na -free solution were exposed to test solutions containing either Na , Li , K , Rb , Cs , Tris , or guanidinium as main cations, folic acid influx was not significantly decreased. Concentration-dependence studies showed that replacement of Na by Rb did not affect the saturable mechanism of folate transport. Rather, a decrease in nonsaturable folic acid uptake accounted for the slightly reduced influx observed in the presence of Rb . Experiments with brush-border membrane vesicles revealed that methotrexate uptake was significantly higher in the presence of external Na than in the presence of K , but was not different from uptake in the presence of K plus valinomycin. These data suggest that 1) the saturable component of folate transportmore » is not Na dependent, and 2) nonsaturable transport of folic acid across the luminal membrane occurs in part through a conductive pathway that involves a negatively charged species of folate and a cation whose membrane permeability affects the rate of folate transport. The importance of Na in this process in vivo derives from the fact that Na is the most permeant cation available at the absorptive site in the small intestine.« less

Authors:
; ;
Publication Date:
Research Org.:
Univ. of Chicago, IL
OSTI Identifier:
6411591
Resource Type:
Journal Article
Journal Name:
Am. J. Physiol.; (United States)
Additional Journal Information:
Journal Volume: 251:2
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; FOLIC ACID; INTESTINAL ABSORPTION; SODIUM CHLORIDES; BIOCHEMISTRY; TRITIUM COMPOUNDS; CARBON 14 COMPOUNDS; CARBOXYLIC ACIDS; CELL MEMBRANES; CESIUM CHLORIDES; IONS; LITHIUM CHLORIDES; METHOTREXATE; POTASSIUM CHLORIDES; RATS; RUBIDIUM CHLORIDES; SMALL INTESTINE; ABSORPTION; ALKALI METAL COMPOUNDS; AMINO ACIDS; ANIMALS; ANTIMETABOLITES; AROMATICS; AZAARENES; BODY; CELL CONSTITUENTS; CESIUM COMPOUNDS; CHARGED PARTICLES; CHEMISTRY; CHLORIDES; CHLORINE COMPOUNDS; DIGESTIVE SYSTEM; DRUGS; GASTROINTESTINAL TRACT; HALIDES; HALOGEN COMPOUNDS; HEMATINICS; HEMATOLOGIC AGENTS; HETEROCYCLIC COMPOUNDS; HYDROXY COMPOUNDS; INTESTINES; LABELLED COMPOUNDS; LITHIUM COMPOUNDS; LITHIUM HALIDES; MAMMALS; MEMBRANES; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANS; POTASSIUM COMPOUNDS; PTERIDINES; RODENTS; RUBIDIUM COMPOUNDS; SODIUM COMPOUNDS; UPTAKE; VERTEBRATES; VITAMIN B GROUP; VITAMINS; 551001* - Physiological Systems- Tracer Techniques

Citation Formats

Zimmerman, J, Selhub, J, and Rosenberg, I H. Role of sodium ion in transport of folic acid in the small intestine. United States: N. p., 1986. Web.
Zimmerman, J, Selhub, J, & Rosenberg, I H. Role of sodium ion in transport of folic acid in the small intestine. United States.
Zimmerman, J, Selhub, J, and Rosenberg, I H. 1986. "Role of sodium ion in transport of folic acid in the small intestine". United States.
@article{osti_6411591,
title = {Role of sodium ion in transport of folic acid in the small intestine},
author = {Zimmerman, J and Selhub, J and Rosenberg, I H},
abstractNote = {The effect of sodium on folate transport across the intestinal luminal membrane was analyzed using two techniques: the influx chamber and isoalted brush-border membrane vesicles. Preincubation of tissue in Na -free medium did not have a consistent effect on folic acid influx provided that Na was present in the test solution. Replacement of Na in the test solution by choline resulted in a significant reduction of folic acid influx. However, when intestinal sheets that had been equilibrated in Na -free solution were exposed to test solutions containing either Na , Li , K , Rb , Cs , Tris , or guanidinium as main cations, folic acid influx was not significantly decreased. Concentration-dependence studies showed that replacement of Na by Rb did not affect the saturable mechanism of folate transport. Rather, a decrease in nonsaturable folic acid uptake accounted for the slightly reduced influx observed in the presence of Rb . Experiments with brush-border membrane vesicles revealed that methotrexate uptake was significantly higher in the presence of external Na than in the presence of K , but was not different from uptake in the presence of K plus valinomycin. These data suggest that 1) the saturable component of folate transport is not Na dependent, and 2) nonsaturable transport of folic acid across the luminal membrane occurs in part through a conductive pathway that involves a negatively charged species of folate and a cation whose membrane permeability affects the rate of folate transport. The importance of Na in this process in vivo derives from the fact that Na is the most permeant cation available at the absorptive site in the small intestine.},
doi = {},
url = {https://www.osti.gov/biblio/6411591}, journal = {Am. J. Physiol.; (United States)},
number = ,
volume = 251:2,
place = {United States},
year = {Fri Aug 01 00:00:00 EDT 1986},
month = {Fri Aug 01 00:00:00 EDT 1986}
}