AJP - Gastrointestinal and Liver Physiology, Vol 239, Issue 1 23-G29, Copyright © 1980 by American Physiological Society
Use of a model of small bowel mucosa to predict passive absorption
D. G. Levitt, J. H. Bond and M. D. Levitt
The purpose of this study was to determine if the observed rate of passive
absorption of inert gases from the canine small bowel could be predicted by
the use of an anatomical model of the mucosa and measurements of villus
blood flow and the diffusive barrier to absorption. Villus blood flow was
measured with microspheres and the diffusive barrier separating bulk
luminal contents and blood was estimated from CO absorption. The model
predicts initial uptake of the inert gases (H2, He, CH4, and 133Xe) in
blood at the villus tip, subsequent countercurrent exchange in the villus,
and longitudinal diffusion of the gases down the villus to a subvillus
blood flow. Observed absorption rates for each of these four gases were
reasonably accurately predicted by the model at both basal villus blood
flow and at low villus blood flow induced by hypotension. We suggest that
this model can be used to predict passive absorption kinetics over a range
of villus blood flows and to predict the influence of a variety of
parameters on the rate of passive absorption of diffusible substances.
