PHI‐like immunoreactivity in the gallbladder and in vitro effect of porcine PHI on smooth muscle of the gallbladder

Abstract

The occurrence and distribution of PHI‐like immunoreactivity in the guinea pig gallbladder has been analysed by radioimmunoassay and immunocytochemistry. Chromatography of gallbladder extracts by gel permeation and high‐performance liquid chromatography revealed that guinea pig PHI‐like immunoreactivity is of a similar size to that of porcine PHI but may differ in its amino acid sequence. Immunocytochemistry showed PHI‐immunoreactivity to be localised to nerves found predominantly in the ganglionated plexus and themucosal plexus of the gallbladder. Pure natural porcine PHI induced a dose‐dependent relaxation of the isolated guinea pig gallbladder muscle which was not blocked by antagonists to acetylcholine, catecholamines, histamine, and 5‐hydroxytryptamine. PHI may thus be one of the local factors involved in controlling gallbladder function.