| Intestinal folate absorption. II. Conversion and retention of pteroylmonoglutamate by jejunum. | |
| | |
MedLine Citation:
|
PMID: 4727453 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
These studies were designed to determine whether pteroylmonoglutamic acid (PGA) at physiologic concentrations is transported across the small intestine unaltered or is reduced and methylated to the circulating folate form (5-methyltetrahydrofolate [5-MeFH(4)]) during absorption. [(3)H]PGA was incubated in vitro on the mucosal side of rat jejunum. Of the folate transferred to the serosal side, the percent identified as 5-MeFH(4) by DEAE-Sephadex chromtography was inversely related to the initial mucosa PGA concentration: at 7, 20, and 2,000 nM, 44%, 34%, and 2%, respectively, was converted to 5-MeFH(4). In contrast, less than 4% of the folate transferred across ileal mucosa was 5-MeFH(4) when the initial mucosa concentration was 20 nM. Specific activity of dihydrofolate (DHF) reductase, the enzyme responsible for converting PGA to tetrahydrofolic acid, was measured in villus homogenates and was significantly greater in the jejunum than in the ileum. 1,000 nM methotrexate (MTX), a DHF reductase inhibitor, markedly inhibited PGA conversion to 5-MeFH(4) by the jejunum. Studies of transmural flux, initial rate of mucosal entry (influx) and mucosal accumulation (uptake) of folate were also performed. Although MTX did not alter the influx of PGA, MTX decreased jejunal mucosal uptake but increased transmural movement. Transmural folate movement across ileal mucosa was greater than across jejunal mucosa although mucosal uptake was greater in the jejunum than in the ileum. These results could explain previous studies which have failed to identify conversion of PGA to 5-MeFH(4) when intestinal preparations have been exposed to higher and less physiologic concentrations of PGA. Further, these studies suggest that 5-MeFH(4) may be retained by the jejunal mucosa. |
| | |
Authors:
|
E J Olinger; J R Bertino; H J Binder |
Related Documents
:
|
4852103 - Functional differentiation of human jejunum and ileum: a comparison of the handling of ... 12973823 - Presystemic metabolism and intestinal absorption of antipsoriatic fumaric acid esters. 11763083 - Multivariate evaluation of factors influencing the performance of a formic acid biosens... |
Publication Detail:
|
Type: Journal Article |
Journal Detail:
|
Title: The Journal of clinical investigation Volume: 52 ISSN: 0021-9738 ISO Abbreviation: J. Clin. Invest. Publication Date: 1973 Sep |
Date Detail:
|
Created Date: 1973-11-01 Completed Date: 1973-11-01 Revised Date: 2009-11-18 |
Medline Journal Info:
|
Nlm Unique ID: 7802877 Medline TA: J Clin Invest Country: UNITED STATES |
Other Details:
|
Languages: eng Pagination: 2138-45 Citation Subset: AIM; IM |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Animals Biological Transport Carbon Isotopes Chromatography, Gel Folic Acid / analysis, metabolism* Folic Acid Antagonists Ileum / enzymology, metabolism Intestinal Absorption* Intestinal Mucosa / enzymology Jejunum / enzymology, metabolism* Male Methane / metabolism Methotrexate / pharmacology Rats Sucrase / analysis Tetrahydrofolate Dehydrogenase / analysis Thymidine Kinase / analysis Time Factors Tritium |
| Chemical | |
Reg. No./Substance:
|
0/Carbon Isotopes; 0/Folic Acid Antagonists; 10028-17-8/Tritium; 59-05-2/Methotrexate; 59-30-3/Folic Acid; 74-82-8/Methane; EC 1.5.1.3/Tetrahydrofolate Dehydrogenase; EC 2.7.1.21/Thymidine Kinase; EC 3.2.1.48/Sucrase |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Contributions of loss of lung recoil and of enhanced airways collapsibility to the airflow obstructi...
Next Document: Interactions between intraluminal bile acids and digestive products on pancreatic and gallbladder fu...