AJP - Gastrointestinal and Liver Physiology, Vol 262, Issue 3 537-G544, Copyright © 1992 by American Physiological Society
Gastric microvascular actions of platelet-activating factor: role of leukocytes
J. G. Wood, Z. Y. Yan and L. Y. Cheung
Department of Surgery, University of Kansas Medical Center, Kansas City 66103.
This study examined the effects of platelet-activating factor (PAF) on the
gastric microcirculation. We measured changes in vascular resistance and
filtration during intra-arterial infusion of graded doses of PAF and its
metabolite, lyso-PAF, to an ex vivo gastric segment of
alpha-chloralose-anesthetized dogs. PAF produced dose-related sustained
increases in vascular resistance (2-150 nM; n = 6). Filtration and venous
hematocrit were also both significantly increased by PAF. In contrast,
there were no statistically significant changes in these measurements with
lyso-PAF (n = 6). Filtration and venous hematocrit were not significantly
changed by norepinephrine at doses that increased perfusion pressure to the
same degree as PAF (n = 4). PAF also increased filtration in the absence of
changes in perfusion pressure (during maximal vasodilation induced with
papaverine). Finally, removal of leukocytes from gastric arterial blood
significantly attenuated these responses to PAF. Our results suggest that
PAF-induced mucosal ischemia is primarily due to vasoconstriction and may
involve edema formation due to increased filtration as well. In addition,
these responses to PAF appear to be largely dependent on circulating
leukocytes.
