Jm. Desesso et Cf. Jacobson, Anatomical and physiological parameters affecting gastrointestinal absorption in humans and rats, FOOD CHEM T, 39(3), 2001, pp. 209-228
Anatomical and physiological parameters of the gastrointestinal (GI) tract
dramatically affect the rate and extent of absorption of ingested compounds
. These parameters must be considered bq nutritionists, pharmacologists and
toxicologists when describing or modeling absorption. Likewise, interspeci
es extrapolation (e,g. from rat to human) requires species-to-species compa
rison of these parameters, The present paper(l) describes the alimentary ca
nal and the barrier to absorption; (2) relates the major sites of absorptio
n: (3) compares the dimensions and surface areas of human and rat intestina
l tracts; (3) discusses motility of the gut and transit times through regio
ns of the alimentary canal: (5) explains how luminal contents are altered b
y physical, chemical and metabolic processes: and (6) describes the flow of
blood and lymph from the GT tract to the systemic circulation, including t
he enterohepatic circulation. Despite strong morphological similarities bet
ween humans and rats at the microscopic level, gross anatomical differences
in the relative absorptive surface areas provide a basis for concluding th
at the human CI tract is capable of absorbing materials faster and to a gre
ater extent than that of the rat. Differences in the environment of the GI
lumen of the two species make it possible to infer which substances are mor
e likely to be present in a dissolved;non-ionized state for each species, T
aken together, these differences may be of sufficient magnitude to alter th
e assessment of risks,benefits for a given compound when those risks/benefi
ts are based on interspecies extrapolations. (C) 2001 Elsevier Science Ltd.
All rights reserved.