AJP - Gastrointestinal and Liver Physiology, Vol 241, Issue 1 24-G30, Copyright © 1981 by American Physiological Society
Permeability of intestinal capillaries to small molecules
M. A. Perry and D. N. Granger
The permeability of capillaries in the isolated, vascularly perfused cat
ileum was studied with the double-indicator diffusion technique. The
molecules studied were raffinose, inulin, and beta-lactoglobulin A. Plasma
flow through the tissue was increased by local intra-arterial infusions of
isoproterenol (a selective mucosal vasodilator) or adenosine (a dilator of
the muscularis vasculature). The permeability-surface area product (PS) for
all solutes increased with increasing plasma flow. At the highest plasma
flow acquired with isoproterenol, PS values for raffinose, inulin, and
beta-lactoglobulin A were approximately 40, 20, and 4 ml.min-1.100 g-1,
respectively. These data suggest that capillaries in the mucosa-submucosa
of the ileum are at least five to seven times more permeable to raffinose
and inulin than has been reported for skeletal muscle capillaries.
Selective vasodilation of the muscularis region with adenosine reduced PS
values for raffinose and inulin at each flow rate studied. The data are
consistent with equivalent pore radii of approximately 60 A for capillaries
in the mucosa-submucosa and 40 A in the muscularis of the small intestine.
