Pyridoxine transport across intestinal cells at high doses
What it found
In lab-grown intestinal cells, high concentrations of pyridoxine moved across the cell layer by passive transport, while low concentrations used an active transport mechanism.
What they found
Animal and lab studies
Transport depends on dose
At low pyridoxine concentrations, the cells used an active transport mechanism. At high concentrations, passive transport dominated.
Direction of movement
At the highest pyridoxine concentration tested, transport from the apical to basolateral side was higher than in the opposite direction.
Cell viability
Even at the highest pyridoxine concentration of 536 micromolar, more than 95% of the 21-day-old cells were alive after 2 hours of exposure.
Comparison with other B vitamins
Pyridoxine showed the same pattern as riboflavin and thiamin: a dual transport mechanism where active transport works at low levels and passive transport takes over at high levels.
What the authors conclude
- They conclude that the transport of pyridoxine is concentration dependent only for low concentrations and independent for high concentrations.
- They advise that for concentrations possible in supplementation tests, passive transport should also be considered.
How it was done
The food and pharmaceutical industries want to know how well B vitamins are absorbed from different sources, and how the transport mechanism changes when vitamins are supplied at high levels, such as in supplements.
They grew Caco-2 intestinal cells on porous membranes for 21 days and measured how pyridoxine moved across the cell layer at concentrations from 87 to 536 micromolar, testing different culture ages, transport directions and temperatures.
What it can’t tell you
- These are lab-grown cells, not people. They can't show what happens in a real human intestine.
- The concentrations tested were much higher than those normally found in the intestine, so the results may not reflect normal dietary intake.
The paper
- Title
- Transport of high concentration of thiamin, riboflavin and pyridoxine across intestinal epithelial cells Caco-2
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Zielińska-Dawidziak M, Grajek K, Olejnik A, Czaczyk K, Grajek W (2008). Transport of high concentration of thiamin, riboflavin and pyridoxine across intestinal epithelial cells Caco-2. Journal of nutritional science and vitaminology. doi:10.3177/jnsv.54.423Free full textPubMed 19155578DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error