An Assessment of the Physiological Importance of the Large Hepatic Venous Sluices in the Dog

Experiments were carried out on isolated canine livers perfused through the hepatic artery and portal vein with blood diluted with Ringer‐Locke solution. Part of the out‐flow was collected from a stiff‐walled catheter which had been wedged in a small tributary of the hepatic venous vein tree and the rest of the outflow was collected from the vena cava. These two collections were measured separately, and it was shown by the injection of histamine, the injection of acetylcholine or by the production of anaphylaxis that an injection which decreased one outflow decreased the other by the same proportional amount. Since the main outflow passed the ostia and would therefore have been impeded had the ostial sphincters constricted strongly it appears that, contrary to reports, the ostial sphincters do not contribute materially to canine hepatic venous resistance. Further experiments in vivo were also carried out where the flow from a wedged hepatic venous catheter was measured. Intraportal injections of acetylcholine and histamine reduced the catheter outflow and it is thought that the small hepatic veins therefore may regulate hepatic venous outflow. It is suggested that the large hepatic veins may function as a small, labile hepatic blood reservoir.