Abstract |
The uptake of riboflavin was studied in everted sacs of rat intestine using [14C] riboflavin and [3H] polyethylene glycol to define the mechanism of mucosal membrane transport. Three-minute incubations were used throughout. Initial studies indicated the presence of saturable uptake in duodenum, jejunum and ileum. Studies in jejunum at low riboflavin concentrations demonstrated saturable uptake [Km = 0.154-0.177 mumol/L, Vmax = 19.6-25.8 pmol/(100 mg dry tissue.min)]. In contrast, uptake was linear with respect to higher concentrations of vitamin (10-50 mumol/L). Uptake at low (0.1 mumol/L) but not high (20 mumol/L) riboflavin concentrations was inhibited by 50 mumol/L lumiflavin, anoxia, 5 mmol/L indoacetamide, Na(+)-free buffer and low temperature (Q10 = 1.64). Conclusions are as follows: 1) Saturable uptake of riboflavin occurs throughout the rat small intestine; 2) uptake by the jejunal mucosa is competitively inhibited and is consistent with a transport carrier located in the brush border membrane; 3) saturable uptake is energy-dependent and may be directly or indirectly driven by a Na+ gradient; and 4) riboflavin is also taken up by rat intestinal mucosa by a nonsaturable, energy-independent mechanism consistent with simple, passive diffusion.
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Authors | H M Middleton 3rd |
Journal | The Journal of nutrition
(J Nutr)
Vol. 120
Issue 6
Pg. 588-93
(Jun 1990)
ISSN: 0022-3166 [Print] United States |
PMID | 2352033
(Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)
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Chemical References |
- Flavins
- lumiflavin
- Sodium
- Riboflavin
- Iodoacetamide
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Topics |
- Animals
- Biological Transport, Active
- Duodenum
(metabolism)
- Flavins
(pharmacology)
- Hypoxia
(metabolism)
- Ileum
(metabolism)
- In Vitro Techniques
- Intestinal Absorption
(drug effects)
- Intestinal Mucosa
(drug effects, metabolism)
- Iodoacetamide
(pharmacology)
- Jejunum
(metabolism)
- Rats
- Rats, Inbred Strains
- Riboflavin
(pharmacokinetics)
- Sodium
(pharmacology)
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