QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mehansho, H. Articles by Henderson, L. M. Search for Related Content PubMed PubMed Citation Articles by Mehansho, H. Articles by Henderson, L. M.

Transport and Metabolism of Pyridoxal and Pyridoxal Phosphate in the Small Intestine of the Rat^1,2,

Department of Biochemistry, University of Minnesota, St. Paul, Minnesota 55108

The transport and metabolism of [³H]pyridoxal (PL) and [³H]pyridoxal-5'-phosphate (PLP) were studied by using isolated, vascularly perfused small intestine of the rat. Physiological levels (0.02 µmole) of the two compounds were administered via the lumen. After a 10 minute experimental period, the amount of isotope removed from the lumen, and the labeled compounds in the lumen, mucosa and perfusate were determined. After 10 minutes about 40% of the radioactivity in PL or PLP had been transported to the perfusate and tissue. Dilution of 0.02 µmole [³H]PL with 20 µmole of unlabeled PL or inhibition with 20 µmole of 4'-deoxypyridoxine did not change the percentage of isotope absorbed, suggesting that the transport of PL occurs by passive diffusion. Substantial amounts of labeled PLP, pyridoxic acid and pyridoxamine phosphate were detected in the mucosa when [³H]PL was administered, but the major form released to the portal circulation was PL. After administration of [³H]PLP, the major labeled vitamer present in the lumen and transported to the perfusate was again PL. This suggested that hydrolysis of PLP occurs in the lumen. Dilution with 20 µmole of unlabeled PLP decreased the percentage of isotope absorbed, reduced dephosphorylation in the lumen and increased the amount of labeled PLP in the mucosa and perfusate. These results imply that at physiological levels PLP is absorbed chiefly as PL, after hydrolysis in the lumen. In addition, PLP is transported across the intestinal wall, but at a slower rate than PL.

KEY WORDS: • pyridoxal • pyridoxal phosphate • transport • metabolism • intestine • vascular perfusion

¹ Supported by USPHS, NIH Grant 5R01-AM19012.

² A preliminary report of this work was presented at the FASEB meeting in Atlantic City, April 1978, (Federation Proc. 79, 652, 1978, Abstr.).

Manuscript received 29 December 1978.