Melatonin alleviated splanchnic hyperdynamic circulation and portosystemic collaterals in cirrhotic rats

Chronic liver damages may end up with cirrhosis and portal hypertension, featured by splanchnic hyperdynamic circulation, angiogenesis, and collaterals formation. Melatonin is used to improve sleep quality, which exerts anti‐inflammatory, anti‐angiogenesis, and vascular actions without significant side effects. However, the relevant impacts on aforementioned derangements are unclear. Liver cirrhosis was induced by bile duct ligation in Sprague‐Dawley rats. The rats received melatonin (40 mg/kg/day, i.p.) or vehicle for 28 days. Experiments were performed on the 28th day when cirrhosis developed. In cirrhotic rats, melatonin treatment significantly increased superior mesenteric artery resistance and reduced the blood flow. Melatonin enhanced the portosystemic collateral responsiveness to arginine vasopressin, reduced mesenteric vascular area, shunting degree, and down‐regulated mesenteric MMP‐2 protein expression. Melatonin improved the splanchnic hyperdynamic circulation, portosystemic collateral shunting, and mesenteric angiogenesis in cirrhotic rats. These beneficial effects make melatonin potentially feasible in clinical setting, but further investigation is required.