EFFECT OF VASOACTIVE INTESTINAL POLYPEPTIDE ON LIVER BLOOD FLOW IN RAT

Abstract

Effects of vasoactive intestinal polypeptide (VIP) on liver blood flow were studied in rats by means of hydrogen gas clearance method using needle electrode. The liver blood flow in control group was 49.2± 3.2ml/min/100g. The administration of 0.002 to 20μg/kg of VIP through the tail vein induced biphasic effects on liver blood flow; 0.2μg/kg of VIP caused 40% increase, while 20μg/kg of VIP induced 30% reduction. However, intraportal administration of VIP showed no changes in liver blood flow. In order to clarify the mechanism of VIP action, the effects of atropine or hexamethonium pretreatment on VIP effects on liver blood flow were examined. The pretreatment with atropine and hexamethonium, which were known as a cholinergic blocker or ganglion blocker, inhibited VIP induced increase of liver blood flow. The administration of anti-VIP antiserum induced no changes in liver blood flow.
These data suggest that VIP increases liver blood flow by acting selectively on hepatic artery and its effects may be mediated via cholinergic systems.