Tubulovesicular transcytotic pathway in isolated rat hepatocyte couplets in culture. Effect of colchicine and taurocholate.

Isolated rat hepatocyte couplets in short-term culture (6 h) were labeled for 3 min with horseradish peroxidase (HRP) to characterize the transcytotic vesicle transport pathway in this cell culture system that retained an "apical" canalicular membrane polarity. Microtubules were identified with monoclonal antibodies to beta-tubulin and fluorescein iso-thiocyanate-labeled goat-antimouse antibody and were concentrated in the apical domain, a structural polarity that was eliminated by pretreatment with colchicine. In control cells, HRP immediately labeled vesicles and tubules in the submembrane regions of the periphery of the cell. Within 10 min tubules and vesicles were prominently labeled in pericanalicular regions, a process blocked by colchicine but not by lumicolchine or taurocholate administration. A quantitative morphometric analysis utilizing a Zeiss Videoplan-2 image analyzer established that (a) HRP-containing structures increased in density, area, length, and diameter in the pericanalicular region by 10 min; (b) colchicine, but not lumicolchicine, pretreatment diminished their density, area, and length; and (c) taurocholate (50 microM), a choleretic and biliary lipid-stimulating bile acid, had no effect on HRP density or percentage of area in the pericanalicular region, but decreased the diameter of the pericanalicular HRP-containing structures and increased the percentage of tubules containing HRP from 29% to 40%. Tubules were particularly prominent in thick sections (400 nm) in both peripheral and pericanalicular regions and were viewed as continuous anastomosing linear arrays in stereo-paired micrographs. These studies established that isolated rat hepatocyte couplets maintain a highly polarized tubulovesicular transcytotic pathway in short-term culture that is micro-tubule-dependent. Taurocholate stimulates the transformation of tubules from vesicles in this isolated rat hepatocyte couplet system.