Neuropeptide levels in murine liver and biliary pathways.

Neuropeptide concentrations in the liver, gallbladder and bile duct of 30 male mice were determined by radioimmunoassay of tissue extracts. Vasoactive intestinal peptide (VIP), substance P, somatostatin, neurotensin, neuropeptide Y (NPY), galanin, gastrin-releasing peptide (GRP) and enkephalin were found in extracts of liver, gallbladder and bile duct. The level of enkephalin was low in all tissues investigated. The most predominant neuropeptide in liver and bile duct was VIP and in the gallbladder, NPY. The function of these neuropeptides in the liver and biliary pathways is unclear. One can speculate, however, that in the liver they regulate blood flow and probably secretion. In the gallbladder and bile duct, they may regulate motility and secretion.