The small bile ducts in the liver of a number of species are enmeshed by a vascular plexus, supplied largely by the hepatic artery (1-3). This peribiliary arterial plexus has been considered by some as evidence that the bile duct epithelia might play an important and active role in the secretion of bile, possibly even to the exclusion of the parenchymal cells (4, 5). In support of this view, it was reported that in the dog the dye sulfobromophthalein sodium (BSP) is removed more completely, and for longer periods of time, when infused into the hepatic artery than when it reaches the liver by way of the portal vein. Since the vascular pathways traversed are common for both routes of injection, except for the intercalation of the peribiliary plexus in the path of part of the arterial blood, this was the site where the extra BSP uptake was thought to take place (6). By way of interpretation the possibility was suggested that BSP is preferentially excreted into bile when taken up by the tissues supplied by this plexus, i.e., by the smaller bile ducts.No direct test of this hypothesis was undertaken, however. With the availability of S35-labeled BSP (7) the possibility suggested itself of using this material in conjunction with nonradioactive BSP to trace quantitatively two simultaneous BSP injections from two injection sites-portal vein and hepatic artery, for example-into bile, and thus to subject the concept of preferential biliary excretion of intra-arterially administered BSP to a critical test.To validate the results of any such experiments requires some further analysis of the qualitative pattern of BSP excretion into bile and of the degree to which this might vary with the route by which the dye reaches the liver, as well as of the * The opinions and assertions contained in this report are the private ones of the writers and are not to be construed as official or reflecting the views of the Navy Department or the Naval Service at large. efficiency with which the dye is removed from arterial and from portal venous blood by the liver in vivo.The present communication will deal with each of these subjects in turn, presenting validating bile secretion studies first, then the simultaneous injection experiments, and finally the extraction efficiency measurements and related studies dealing with the problem of obtaining representative hepatic vein samples.
METHODSThe experiments were carried out on female mongrel dogs, 9.5 to 15.0 Kg., which had been maintained in the laboratory on commercial canned dog food for at least six weeks. They were free of acute disease, and histopathological examination showed the livers of all animals used in these experiments to be free of significant abnormalities. Intravenous sodium pentobarbital anesthesia was employed throughout, respiratory rates being maintained between 14 and 20 per minute. Rectal temperatures were maintained above 35.5°C., if necessary, by the use of hot pads; in any one animal rectal temperature fluctuations did not exceed a range of 2.5°C.Injections were made ...