title: Microscope laser light-scattering spectroscopy of vesicles within canaliculi of rat hepatocyte couplets.
abstract: Employing microscope laser light-scattering spectroscopy, we investigated "primary" bile secretion into canalicular spaces of rat hepatocyte couplets in monolayer culture. Time-dependent scattered light intensities were fitted by bi-exponential decays. The "slow" decay was attributed to an undulating canalicular membrane motion, whereas the "fast" decay was consistent with rapidly diffusing intracanalicular vesicles with mean hydrodynamic radii (+/- SD) of 479 +/- 53 A. After addition of micromolar concentrations of common bile salts, increases in the amplitude of the fast component facilitated a quantitative estimate of vesicle secretion rates. A dose-response relationship with 0.1-200 microM sodium taurocholate was characterized by an initial concentration-dependent increase and then a decrease in the amplitude of the fast canalicular component. Since these taurocholate concentrations are nontoxic to cultured hepatocytes, the maximum in vesicle-sized particles at 10 microM taurocholate suggested that its critical micellar concentration of approximately 5 mM was attained within the canalicular spaces. Sodium taurolithocholate resulted in time- and dose-dependent diminution in vesicle secretion rates, which after 2 h was followed by spontaneous canalicular recovery. This suggested that acute bicellular "cholestasis" was followed by oxidative metabolism and detoxification of the monohydroxy bile salt. Microscope laser light-scattering spectroscopy should facilitate further physical-chemical and pathophysiological studies of bile secretion at the cellular level.
authors.affiliation: Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Möckel
authors.forename: S
authors.initials: S
authors.lastname: Gorti
authors.forename: R K
authors.initials: RK
authors.lastname: Tandon
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
authors.forename: M C
authors.initials: MC
authors.lastname: Carey
mesh_terms: D000818:Animals; D001646:Bile / Q000187:drug effects / Q000378:metabolism; D001647:Bile Acids and Salts / Q000494:pharmacology; D001648:Bile Canaliculi / Q000187:drug effects / Q000648:ultrastructure*; D002478:Cells, Cultured; D015638:Cytochalasin D / Q000494:pharmacology; D007834:Lasers; D050356:Lipid Metabolism; D008099:Liver / Q000166:cytology / Q000648:ultrastructure*; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D017207:Rats, Sprague-Dawley; D012542:Scattering, Radiation; D013656:Taurocholic Acid / Q000494:pharmacology; D013658:Taurolithocholic Acid / Q000494:pharmacology
chemical_list: D001647:Bile Acids and Salts; D015638:Cytochalasin D; D013658:Taurolithocholic Acid; D013656:Taurocholic Acid