Studies concerning functional differences between liver regions supplied by the hepatic artery and by the portal vein.

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