Neuronal and non-neuronal choline ester hydrolases in the rabbit liver

Biochemical and histochemical methods have been used to determine both activity and distribution of choline ester hydrolases in the rabbit liver. Acetylcholinesterase was detected in kupffer cells, predominantly in th centri- and mid-lobular regions. Neither the activity nor the distribution of acetylcholinesterase activity was influenced by the intravenous injection of zymosan or the iron-dextran complex imferon on at dosages known to stimulate reticuloendothelial phagocytic function. Although this finding suggests that acetylcholinesterase is not primarily concerned with the pocesses of phagocytosis, there exists the possibility that reticuloendothelial acetylcholinesterase may have a function in metabolism of phagocytosed lipids and esters. Butyrylcholinesterase was present in both hepatocytes and the intrinsic hepatic nerves. Polarization of hepatocyte butyrylcholinesterase activity was noted; the enzyme activity being most marked in the centrilobular hepatocytes. Hepatocyte butyrylcholinesterase activity was unaffected by the intravenous administration of zymosan or imferon. The intrinsic hepatic nerves were present only in portal tracts and interlobular septa, there being no evidence for the existence of an hepatic parenchymal plexus. These findings by cholinesterase histochemistry were confirmed by controlled neurohistological techniques. The morphological findings suggest that the intrinsic hepatic nerves regulate blood flow through the organ and are possible sensory to the bile ducts.