Development of the Bile Canalicular System in Rat Liver: with Special Reference to Bile Canalicular Actin Filaments and Mg2+, Ca2+-ATPase Activity.

Abstract

Developmental changes of the bile canaliculi (BC) in rat (fetal 13th-21st day, postnatal and adult) livers were cytochemically examined by fluorescence, light and electron microscopy. Bile canalicular actin filaments (F-actin), consisting of the circumferential pericanalicular F-actin and microvilli (MV) core F-actin, were observed by 7-nitrobenz-2-oxa-1,3-diazole phallacidin (NBD-ph) fluorescence microscopy and electron microscopy. Mg2+, Ca2+-ATPase activity, which is presumed to be involved in bile acid secretion across the bile canalicular membrane, was detected by a modified Wachstein and Meisel method at both light and electron microscopic levels. Bile canalicular F-actin sparsely appeared from the 13th day of gestation. Since then, the amount of bile canalicular F-actin gradually increased accompanying the bile canalicular formation by 2 weeks after the birth when the development was almost completed. Mg2+, Ca2+-ATPase activity appeared on the fetal 19th day in less than 10% of the BC. The number of Mg2+, Ca2+-ATPasepositive BC rapidly increased around the time of birth (fetal 21st day-postnatal 1st day). The rate of ATPase positive BC reached 40-70% during this period. On the 5th day after birth, most BC showed Mg2+, Ca2+-ATPase activity. These findings indicated that the expression of bile canalicular F-actin and ATPase can be regarded as a structural marker and a functional marker for bile secretion, respectively. Structural development of BC began earlier but at a rather slower rate than functional maturation.

Intracellular calcium stores and inositol 1,4,5-trisphosphate receptor in rat liver cells

“…In the present work, the Ins(1,4,5)P $ receptor was localized beneath the PM, along the canalicular domain and to a lesser extent along the sinusoidal domain. This localization resembled the labelling of F-actin with NBD-phalloidin in liver sections, where the bile canalicular area appeared strongly fluorescent and the sinusoidal and lateral membranes were also moderately positive [62]. Thus the liver Ins(1,4,5)P $ receptor could be more or less directly associated with the actin filaments, as has been found in cultured keratinocytes [63].…”

Disturbed structural interactions between microfilaments and tight junctions in rat hepatocytes during extrahepatic cholestasis induced by common bile duct ligation

“…Fluorescence microscopy of F-actin and ZO-1 F-actin was demonstrated according to the method of Lee et al (1993) with some modifications. Cryostat sections (7-µm-thick) were treated with 0.03% saponin in PHEM buffer (60 mM PIPES, 25 mM HEPES, 10 mM EGTA, 2 mM MgCl 2 , pH 6.8) containing 1 mM phenylmethysulfonyl fluoride (PMSF; Sigma, St. Louis, Mo., USA), 5 µM leupeptin (Sigma), and 8% sucrose, for 7 min at 22°C.…”

Rearrangement of hepatocellular F-actin precedes the formation of rosette-like structures in parenchyma of cholestatic rat liver

“…Fluorescence Microscopy of F-Actin. F-actin was shown through light microscopy, according to the procedure of Lee et al 19 with some modifications. Cryostat sections (7 and 30 µm thick) were extracted with 0.03% saponin in PHEM buffer (60 mmol/L Pipes, 25 mmol/L HEPES, 10 mmol/L EGTA, and 2 mmol/L MgCl 2 [pH 6.8]) containing 1 mmol/L phenylmethysulfonyl fluoride (Sigma), 5 µmol/L leupeptin (Sigma) and 8% sucrose, for 7 minutes at 22°C.…”