A STUDY OF HEPATIC HEMODYNAMICS IN THE DOG

The effects of altered hepatic blood flow, of splanchnic and hepatic nerve stimulation, and of injecting epinephrine and vasopressin (Pitressin) were studied by perfusing canine livers in vitro. Controlled hepatic arterial perfusions demonstrated a linear relationship between arterial pressure and hepatic arterial inflow. It was found that increases of hepatic artery flow slightly increased portal vein pressure and vascular resistance of the portal vein, and that increases of portal vein flow slightly increased hepatic artery vascular resistance. Splanchnic nerve stimulation caused vasoconstriction of the hepatic artery, portal vein, and mesenteric vasculature. Hepatic nerve stimulation caused constriction of only the hepatic artery and portal vein vasculature. Similar results were obtained by the administration of epinephrine. Pitressin caused marked vasoconstriction of the mesenteric vasculature, vasodilatation of the portal vein vascular bed, and slightly increased hepatic artery vasomotor tone. It was noted that the rise in portal vein vasomotor tone with sympathetic stimulation was due in part to constriction of the "postjunctional" resistance.

INTESTINAL AND HEPATIC TRANSPORT OF CHOLATE AND ORGANIC DYES

The 3-hr cumulative biliary appearance of a bile salt and three representative organic dyes was studied in rats anesthetized with sodium pentobarbital. The substances were administered in one of the following locations: a branch of the portal vein, a 20-cm isolated loop of proximal jejunum, or a similar loop of distal ileum. Average biliary recoveries of 10 mg cholate, bromsulfonphthalein, diiodotetrachlorofluorescein (rose bengal) or phenolsulfonphthalein (phenol red) introduced slowly into the portal circulation were 97, 97, 68, and 23%, respectively. The respective recoveries of 30-mg quantities of these four substances placed in the intestinal loops were 43, 5, 2, and 1% proximally and 90, 5, 5, and 0.4% distally. These observations confirm the presence of a specific intestinal transport mechanism for cholate with maximal activity in the distal ileum. However, the three representative organic dyes are shown not to be carried by the intestinal bile salt transport mechanism and their movement from gut lumen to portal vein blood should be ascribed to a passive process.

INTRAHEPATIC VASCULAR AND BILE-DUCT SYSTEMS AS RELATED TO OPERATIVE TREATMENT OF BILE-DUCT ATRESIA

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THE NATURE OF TRANSCAPILLARY EXCHANGE IN THE LIVER

The nature of transcapillary exchange in the liver was explored by applying the single-injection multiple-indicator dilution technique to the liver. Labelled red cells and a group of passively distributed substances were introduced into the portal vein in the dog. The diffusible substances were delayed during their passage through the liver and the outflow pattern produced by the delay was found, in each case, to correspond to that situation in which the diffusion of these substances across the sinusoidal wall was so rapid in relation to flow that it could be considered complete at every point along the length, a situation which may be termed flow-limited. The calculated volume of distribution for water corresponded to the actual water volume in the excised liver. The volume of distribution for the extracellular diffusible substances was shown to decrease with increase in molecular weight.