Distribution of intravenously injected secretin in the liver and its internalization into the bile epithelial cells

Abstract

In order to clarify the actual effective site of secretin in the liver, the distribution of intravenously injected secretin was examined in dogs using a specific antisecretin antibody. The localization of secretin was examined with immunofluolescent and immunoperioxidase method and observed with light and electron microscopy serially after secretin injection.
By the immunofluorescent method, the fluorescence was already observed on the basolateral surface of ductal cells with various sizes compatible with bile ductules to septal ducts as early as 3 minutes after secretin injection, showing that the secretin receptor exists in all size of bile ducts.
By the immunoperioxidase method, the light microscopic observation revealed a diffuse staining in the cytoplasma of the ductal cells 20 minutes after secretin injection. Electron microscopic observation revealed a dominant staining of the basolateral plasma membrane, endoplasmic reticulum and intercellular vesicles, which suggested the positive uptake of secretin into the ductal cells.