Uremia increases gastric mucosal permeability and acid back-diffusion injury in the rat.

The possibility that chronic uremia renders the gastric mucosa more susceptible to acid injury was investigated. A rat model of chronic renal failure was induced by subtotal nephrectomy. [H+] back-diffusion across the mucosa, following intragastric perfusion of 0.15N HCl or 15% ethanol in 0.15N HCl, was significantly greater in uremic than in sham-operated rats. Gastric mucous gel thickness and transmural potential difference were significantly lower in rats with renal insufficiency. Furthermore, a significantly greater acidification rate of the surface epithelial cells was found in uremic rats than in sham-operated rats during superfusion with pH 1.7 buffer. Intragastric administration of acidified ethanol or aspirin solutions markedly increased gastric mucosal blood flow (68% and 89% respectively) in the sham-operated group producing mild injury, in contrast to uremic rats, where a lesser increase in mucosal blood flow (7% and 14% respectively) was associated with more pronounced mucosal injury. It was concluded that enhanced susceptibility to acid injury in uremia is due to a reduction of function of pre-epithelial, epithelial, and postepithelial elements of the gastric mucosal barrier.