The technique we have developed for studying absorption of marker compounds from the biliary tree is called segmented retrograde intrabiliary injection (SRII). This technique is applied to rats to demonstrate changes in the biliary tree epithelium. Inert marker compounds such as mannitol are used to demonstrate permeability changes. For instance, we will use a variety of bile salts to effect changes in permeability. The ability of the different bile salts to increase permeability will be compared. We know from preliminary work that dehydrocholate does not affect mannitol recovery as much as do other bile salts such as glycocholate and taurocholate. Also both of the latter decrease intrabiliary pressure whereas dehydrocholate has little effect on intrabiliary pressure. By both recovery and the intrabiliary pressure changes, certain bile salts will be shown to increase bile epithelial permeability. As we have shown in present studies that the SRII technique can be used to demonstrate the existence of a glucose reabsorptive carrier system in the biliary tree, we will use the SRII technique to test whether a carrier system exists for absorption of amino acids from bile. In other test systems, the absorptive specificity of the amino acids fall into several classes. We will see whether carriers for the biliary systems have similar specificities.