Effect of lithium on ionic balance and polyphosphoinositide metabolism during larval vegetalization of the sea urchin Paracentrotus lividus

BACKGROUND: Intragastric hypertonic (2 mol/L) saline produces injury in the gastric mucosa and a significant increase in gastric blood flow (hyperemia) in anesthetized rats. We studied the mechanism of this hyperemia. METHODS: Rats were treated with intravenous boluses of NG-nitro-L-arginine methyl ester (3 mg/kg) to block synthesis of endogenous nitric oxide, pyrilamine (1 mg/kg) to inhibit H1 receptors, or indomethacin (5 mg/kg) to block synthesis of endogenous prostaglandins during blood flow studies or with subcutaneous capsaicin (125 mg/kg) 10-14 days before blood flow studies to ablate capsaicin-sensitive afferent nerves. Gastric mucosal blood flow was measured by hydrogen gas clearance before and during intragastric administration of 2 mol/L saline. RESULTS: The gastric hyperemia induced by intragastric 2 mol/L saline was completely blocked only by indomethacin. The associated gastric mucosal damage was increased significantly. CONCLUSIONS: In the rat stomach, the gastric hyperemia induced by intragastric 2 mol/L saline is mediated by endogenous prostaglandins and plays a protective role. Endogenous nitric oxide, H1 receptors, and capsaicin-sensitive afferent nerves are not involved in this protective hyperemia.