Hepatic metabolism of vasoactive intestinal polypeptide during liver transplantation in the pig

In order to investigate hepatic clearance of vasoactive intestinal polypeptide we measured its concentration in blood from the common carotid artery, right atrium and portal vein during orthotopic liver transplantation in six pigs. Just after laparotomy we found a significantly higher concentration of vasoactive intestinal polypeptide in portal plasma compared to that of the right atrium (p less than 0.05). This difference was soon eliminated by a fall in portal concentration, and, apart from fluctuations in portal concentration, no significant gradient between portal and atrial blood was recorded during the remaining part of the operation. When portal concentrations exceeded 30 pmol/l, the median reduction after transhepatic passage was 29% (range 16.8%-63.9%), while portal concentrations less than 30 pmol/l had a median reduction of only 6.3% (range 1.4%-16.5%) (p less than 0.05). No gradient between right atrial and systemic arterial blood was recorded. We suggest that a concentration-dependent clearance of splanchnic vasoactive intestinal polypeptide takes place in the porcine liver.