THE ACINAR LOCATION OF THE SODIUM-INDEPENDENT AND THE SODIUM-DEPENDENT COMPONENT OF TAUROCHOLATE UPTAKE - A HISTOAUTORADIOGRAPHIC STUDY OF RAT-LIVER

The acinar location of tritium-labelled taurocholate taken up from sodium-containing and sodium-free perfusion media in isolated perfused rat liver was made visible by means of histoautoradiography on cryoslices at low, medium and high bile salt concentrations. In antegrade perfusion studies, in the presence of sodium, with taurocholate concentrations of 1 and 20-mu-M, respectively, the silver grain label was mainly restricted to acinar zones 1. At an 80-mu-M concentration, zones 2 and 3 were also labelled but with decreasing intensities towards the terminal hepatic venules. At 120-mu-M taurocholate, all acinar zones were nearly equally labelled. In the absence of sodium, antegrade liver perfusions with 1, 20 and 120-mu-M taurocholate resulted in an almost homogenous labelling of all acinar zones and retrograde perfusions in a silver grain density slightly decreasing towards the terminal portal venules. The results indicate that hepatocytes of all acinar zones are capable of taking up taurocholate by both a sodium-dependent and a sodium-independent pathway. The contribution of the sodium-independent uptake to the overall uptake of taurocholate increases with increasing zonal recruitment at higher concentrations. The sodium-dependent uptake, however, is always dominant.