The role of blood flow in gastric mucosal defence, damage and healing.

Blood flow plays an important role in protection of normal gastric mucosa and in the protection and healing of damaged mucosa. Blood flow contributes to protection by supplying the mucosa with oxygen and HCO3-, and by removing H+ and toxic agents diffusing from the lumen into the mucosa. Low mucosal blood flow predisposes to injury, whereas high blood flow protects against injurious agents. Superficial mucosal damage is followed by increased blood flow which supports the healing process and prevents superficial lesions from developing into deep ones. The hypermic response increases the supply of HCO3- to the mucosa and increases the resistance of the injured mucosa against back diffusing H+ and aggressive drugs such as ethanol (adaptive protection). Mucosal ischemia contributes to gastric ulceration in various clinical conditions such as hemorrhagic shock, stress, aorta aneurysm and after proximal gastric vagotomy. Blood vessels are damaged in gastric ulcers. During ulcer healing blood flow returns to normal. Stimulated or inhibited angiogenesis in the granulation tissue effects the healing of a gastric ulcer.