On the mechanism of human intestinal absorption.
In order to investigate whether the main step in intestinal absorption in humans is dominated by partition or by diffusion, we have transformed % human intestinal absorption into a first-order rate constant, and have regressed the latter, as logk, against our solvation parameters. The obtained regression coefficients are compared with those for diffusion and partition processes. The coefficients in the logk equation are completely different to those for water/solvent partitions, but are very similar to those for processes (not involving transport through membranes) in which diffusion is the major step. It is suggested that the main step in the absorption process is diffusion through a stagnant mucus layer, together with transfer across the mucusmid R:membrane interface. It is further shown that for strong Bronsted acids and bases, the rate constant for absorption of ionic species is close to that for absorption of the corresponding neutral species, so that to a first approximation the % intestinal absorption can be calculated from properties of the neutral species.
Abraham
Michael H
MH
Department of Chemistry, University College London, 20 Gordon Street, WC1H OAJ, London, UK. m.h.abraham@ucl.ac.uk
Zhao
Yuan H
YH
Le
Joelle
J
Hersey
Anne
A
Luscombe
Christopher N
CN
Reynolds
Derek P
DP
Beck
Gordon
G
Sherborne
Brad
B
Cooper
Ian
I
D001692:Biological Transport; D004058:Diffusion; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007408:Intestinal Absorption; D007477:Ions; D007700:Kinetics; D008954:Models, Biological; D012997:Solvents
D007477:Ions; D012997:Solvents