AJP - Gastrointestinal and Liver Physiology, Vol 246, Issue 6 654-G659, Copyright © 1984 by American Physiological Society
Effect of topical histamine on mucosal microvascular permeability and acid secretion in the rat stomach
H. Nagata and P. H. Guth
The effect of topical histamine on microvascular permeability to
macromolecules was studied in the rat gastric mucosa using a fluorescent in
vivo microscopy technique. Acid secretion was measured in the
pylorus-ligated rat. A topical dose of 10(-2)M histamine increased acid
output to a maximum, which was equal to the maximum values attained by
intravenous or subcutaneous histamine. Only in rats pretreated with a
beta-adrenergic antagonist did 10(-2) to 5 X 10(-2)M histamine cause leak
of a fluorescein-albumin conjugate from mucosal microvessels. Leak occurred
around collecting venules but not from capillaries. An H1-receptor
antagonist, but not an H2-receptor antagonist, significantly decreased
histamine-induced leaks. We concluded the following. 1) topically applied
histamine penetrates into the mucosa and can increase acid secretion to the
same extent as parenteral histamine. 2) Topical histamine increases
microvascular permeability to macromolecules only when beta-adrenergic
receptors are blocked. Larger doses of histamine are needed for initiating
the permeability change than for initiating the acid secretory response. 3)
H1-receptors in venules are involved in the histamine-induced increase in
permeability.
