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Uptake of Pyridoxine Hydrochloride by the Rat Jejunal Mucosa in vitro^1,2,

Gastroenterology Research Laboratories, Veterans Administration Hospital (FHD), and the Department of Medicine, Medical College of Georgia, Augusta, Georgia 30904

The kinetics of mucosal membrane transport of pyridoxine hydrochloride were evaluated in vitro in the rat jejunum. Utilizing everted sacs and a double-label isotope technique, short-term incubation within the period of initial linear tissue uptake indicated: 1) no evidence of saturation of uptake over a wide pyridoxine · HCl concentration range (0.01 µM–10 mM); 2) failure of 4-deoxypyridoxine (10 µM), anoxia, iodoacetamide (5 mM), Na⁺ replacement, and ouabain (1 mM) to inhibit uptake of 2 µM pyridoxine · HCl significantly; and 3) a low Q₁₀ value of 1.31. Using singlelabel techniques, sacs were also incubated for 1 hour in 2 µM pyridoxine HCl with determination of the apparent tissue water-mucosal fluid concentration ratio and chromatographic separation of the various forms of vitamin B₆ in tissue. Results demonstrated a failure of pyridoxine in tissue water to achieve a concentration in excess of that in the incubation medium. Data, therefore, were most consistent with passive diffusion as the mechanism for in vitro jejunal mucosal uptake of pyridoxine · HCl in the rat.

KEY WORDS: • pyridoxine • transport • jejunum

¹ This study was supported by the Veterans Administration (MRIS #5702).

² Published in abstract form in Clin. Res. 24, 12A, 1976.

Manuscript received 4 May 1976.

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