TY - JOUR
T1 - Transport of the biotin dietary derivative biocytin (N-biotinyl-l-lysine) in rat small intestine
AU - Said, Hamid M.
AU - Thuy, Le Phuc
AU - Sweetman, Larry
AU - Schatzman, Benjamin
PY - 1993/1
Y1 - 1993/1
N2 - Background: Biocytin is an important end product of intraluminal digestion of dietary protein-bound biotin. Limited studies are available regarding the ability of the small intestine to transport biocytin and about the mechanism involved. The aim of the present study was to delineate these issues. Methods: Transport of [3H]-biocytin was examined using everted sacs from rat intestine. Results: Mucosal-to-serosal transport of low (0.022 μmol/L) and high (5 μmol/L) concentrations of biocytin were linear for up to 20 minutes of incubation. Transport of biocytin as a function of concentration (0.022-5 μmol/L) was linear (r = 0.99) and occurred at a rate of 22,062 fmol · g tissue (wet wt)-1 · 15 min-1. Addition of high concentrations of unlabeled biocytin, biotin, biotin methyl ester, and lysine did not cause a significant inhibition of the transport of [3H]-biocytin. Furthermore, transport of biocytin was independent of Na+ concentration, pH, energy, and temperature. Compared with transport of equimolar concentrations of free biotin, transport of biocytin (0.022 μmol/L) was significantly lower in both the jejunum and the ileum. Conclusions: (1) Biocytin transport in rat intestine is lower than that of free biotin and occurs via simple physical diffusion. (2) In the rat, efficient absorption and optimal bioavailability of dietary protein-bound biotin necessitates its conversion to free biotin.
AB - Background: Biocytin is an important end product of intraluminal digestion of dietary protein-bound biotin. Limited studies are available regarding the ability of the small intestine to transport biocytin and about the mechanism involved. The aim of the present study was to delineate these issues. Methods: Transport of [3H]-biocytin was examined using everted sacs from rat intestine. Results: Mucosal-to-serosal transport of low (0.022 μmol/L) and high (5 μmol/L) concentrations of biocytin were linear for up to 20 minutes of incubation. Transport of biocytin as a function of concentration (0.022-5 μmol/L) was linear (r = 0.99) and occurred at a rate of 22,062 fmol · g tissue (wet wt)-1 · 15 min-1. Addition of high concentrations of unlabeled biocytin, biotin, biotin methyl ester, and lysine did not cause a significant inhibition of the transport of [3H]-biocytin. Furthermore, transport of biocytin was independent of Na+ concentration, pH, energy, and temperature. Compared with transport of equimolar concentrations of free biotin, transport of biocytin (0.022 μmol/L) was significantly lower in both the jejunum and the ileum. Conclusions: (1) Biocytin transport in rat intestine is lower than that of free biotin and occurs via simple physical diffusion. (2) In the rat, efficient absorption and optimal bioavailability of dietary protein-bound biotin necessitates its conversion to free biotin.
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U2 - 10.1016/0016-5085(93)90837-3
DO - 10.1016/0016-5085(93)90837-3
M3 - Article
C2 - 8419264
AN - SCOPUS:0027475939
SN - 0016-5085
VL - 104
SP - 75
EP - 80
JO - Gastroenterology
JF - Gastroenterology
IS - 1
ER -