AJP - Gastrointestinal and Liver Physiology, Vol 270, Issue 3 487-G491, Copyright © 1996 by American Physiological Society
Measurements of the jejunal unstirred layer in normal subjects and patients with celiac disease
A. Strocchi, G. Corazza, J. Furne, C. Fine, A. Di Sario, G. Gasbarrini and M. D. Levitt
I Patologia Medica, University of Bologna, Italy.
Normal intestinal absorption of nutrients requires efficient luminal mixing
to deliver solute to the brush border. Lacking such mixing, the buildup of
thick unstirred layers over the mucosa markedly retards absorption of
rapidly transported compounds. Using a technique based on the kinetics of
maltose hydrolysis, we measured the unstirred layer thickness of the
jejunum of normal subjects and patients with celiac disease, as well as
that of the normal rat. The jejunum of humans and rats was perfused with
varying maltose concentrations, and the apparent Michaelis constant (Km)
and maximal velocity (Vmax) of maltose hydrolysis were determined from
double-reciprocal plots. The true Km of intestinal maltase was determined
on mucosal biopsies. Unstirred layer thickness was calculated from the in
vivo Vmax and apparent Km and the in vitro Km of maltase. The average
unstirred layer thickness of 11 celiac patients (170 micron) was seven
times greater than that of 3 controls (25 micron). The unstirred layer of
each celiac exceeded that of the controls. A variety of factors could
account for the less efficient luminal stirring observed in celiacs.
Although speculative, villous contractility could be an important stirring
mechanism that would be absent in celiacs with villous atrophy. This
speculation was supported by the finding of a relatively thick unstirred
layer (mean: 106 micron) in rats, an animal that lacks villous
contractility. Because any increase in unstirred layer slows transport of
rapidly absorbed compounds, poor stirring appears to represent a previously
unrecognized defect that could contribute to malabsorption in celiac
disease and, perhaps, in other intestinal disorders.
