Effects of platelet-activating factor on canine gastric mucosal blood flow and permeability to luminal acid

Recent studies suggest that platelet-activatingfactor, a newly described phospholipid released during acute inflammation, may predispose the gastric mucosa to acute ulceration. This study was performed to evaluate whether this substance might contribute to acute injury through its effects on mucosal microcirculation or by increasing permeability of the gastric mucosa to luminal acid. Platelet-activating factor was infused at a rate of 1 μg/min directly into the artery supplying a chambered segment of canine gastric corpus and both significantly decreased venous outflow and mucosal blood flow and enhanced the efflux of volume, sodium ions, and potassium ions into the lumen. Thus, as in other capillary beds, platelet-activating factor appeared to induce stasis of flow and local accumulation of interstitial fluids which then leaked into the lumen. Platelet-activating factor did not significantly alter the back-diffusion of hydrogen ions into the mucosa. Thus, platelet-activating factor may not directly influence mucosal permeability to luminal acid, and it may predispose the gastric mucosa to acute injury through its effects on the microvasculature and other aspects of the inflammatory process.