AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 2 201-G207, Copyright © 1983 by American Physiological Society
Effect of histamine on microvascular permeability in the rat stomach
H. Nagata and P. H. Guth
The effect of histamine on gastric microvascular permeability to
macromolecules in the rat was studied using fluorescent in vivo microscopy.
Histamine was applied topically to the serosal surface for study of the
muscularis externa, to the submucosa, and to the superficial mucosa, and
the area of leaks of a fluorescein-albumin conjugate from microvessels was
quantitated. In the muscularis externa both histamine and an H1-agonist,
but not an H2-agonist, caused dose-dependent leak of conjugate from
venules. An H1-antagonist, but not an H2-antagonist, decreased the
histamine-induced leak. In the submucosa histamine caused dose-dependent
dilatation of arterioles but not leak of conjugate. In contrast, bradykinin
caused both dose-dependent dilatation of arterioles and leak of conjugate
from venules. In the superficial mucosa histamine did not cause any leak.
In conclusion, topical histamine 1) increased microvascular permeability to
macromolecules from venules in the muscularis externa via H1-receptors, 2)
did not affect microvascular permeability in the submucosa (this may be due
to lack of histamine receptors on the venules as bradykinin increased
venular permeability), and 3) did not affect microvascular permeability in
the superficial mucosa, but there might not have been adequate histamine
backdiffusion.
