Protein composition of rat bile.

In order to characterize the protein composition of rat bile, the bile duct was cannulated in 250 g male Wistar rats and biliary proteins were examined over 48 h. Total protein secretion was monitored by the Cu2+--Folin differential test while individual proteins were characterized by sodium dodecyl sulfate (SDS) and non-SDS polyacrylamide gel electrophoresis. The relative contribution of various proteins was evaluated by densitometric scanning of the stained gels. It was observed that both total biliary protein secretion and the protein polypeptide profiles remained constant throughout the 48h. This is in comparison with biliary bile-acid secretion which fluctuates markedly during this time period both in quantity and composition. It is concluded that biliary secretion is probably not related to the biliary secretion of bile acids.