Localization of alkaline phosphatase and proteins related to intercellular junctions in primary cultures of fetal rat hepatocytes

Abstract

The localization of alkaline phosphatase (ALP) and four proteins related to intercellular junctions in primary cultures of fetal rat hepatocytes was immunocytochemically investigated using fluorescence-labeled antibodies and confocal laser microscopy in order to determine whether the formation of intercellular junctions at the borders between adjacent rat hepatocytes becomes the trigger of translocation of ALP from the cytoplasm to the plasma membrane. Dexamethasone (DEX) which was supplemented in the base medium promoted the translocation of ALP from the cytoplasm to the plasma membrane surrounding bile canaliculus-like intercellular spaces and the appearance of connexin-32 at cell borders between adjacent fetal hepatocytes. E-cadherin, occludin and ZO-1 were localized at the cell borders between adjacent fetal hepatocytes irrespective of the presence of DEX. Occludin and ZO-1 were further localized along the plasma membrane surrounding bile canaliculus-like intercellular spaces formed by DEX. The present study indicates that the formation of adherens and tight junctions between adjacent rat hepatocytes does not become the trigger of ALP translocation from the cytoplasm to the plasma membrane, although we cannot be certain of whether the formation of gap junctions between adjacent rat hepatocytes triggers ALP translocation.

Localization of Alkaline Phosphatase and Cathepsin D during Cell Restoration after Colchicine Treatment in Primary Cultures of Fetal Rat Hepatocytes

“…1B). We previously demonstrated that the long stretches of plasma membrane exhibiting ALP localization between cell borders of normal hepatocytes are those surrounding the bile canaliculus-like structure, as the bile canaliculus marker occludin is colocalized in these long stretches of plasma membrane [5]. On the other hand, CAPD was observed in small scattered dots in the cytoplasm (Fig.…”

Change in Localization of Alkaline Phosphatase and Mannosidase II by Colchicine Treatment of Primary Cultures of Fetal Rat Hepatocytes

“…It has been reported that, in monolayer culture systems, adult rat hepatocytes cultured on a single collagen gel rapidly dedifferentiate, but cells sandwiched between two layers of collagen gel maintain cellular morphology and function for long periods [ 18 , 21 ]. However, in the present culture system of fetal rat hepatocytes, dexamethasone induced GGT translocation, the formation of bile canaliculus-like structures and the appearance of connexin 32 at cell borders [ 6 , 10 , 13 ]. The above results coincided with those reported in primary rat hepatocytes overlaid with a basement membrane-like matrix extracted from Engelbreth-Holm-Swarm mouse tumor [ 25 ].…”

“…Alkaline phosphatase (ALP) in rat hepatocytes is mainly localized in the plasma membrane surrounding the bile canaliculus [ 1 , 4 , 14 , 33 , 34 ] and hydrolyzes the phospholipids in bile excreted by hepatocytes into the bile canalicular lumen [ 27 ]. Previous papers have reported that dexamethasone, in primary cultures of fetal rat hepatocytes, promotes formation of the bile canaliculus-like structure [ 6 ] and translocation of ALP from the limited perinuclear cytoplasm to the plasma membrane surrounding the bile canaliculus-like structure [ 10 , 13 ]. Moreover, in the same culture system, it was demonstrated that dexamethasone represses DNA synthesis [ 6 ] and promotes the appearance of connexin 32 between adjacent hepatocytes [ 10 , 13 ].…”

“…Previous papers have reported that dexamethasone, in primary cultures of fetal rat hepatocytes, promotes formation of the bile canaliculus-like structure [ 6 ] and translocation of ALP from the limited perinuclear cytoplasm to the plasma membrane surrounding the bile canaliculus-like structure [ 10 , 13 ]. Moreover, in the same culture system, it was demonstrated that dexamethasone represses DNA synthesis [ 6 ] and promotes the appearance of connexin 32 between adjacent hepatocytes [ 10 , 13 ]. These observations indicate that hepatocyte differentiation promotes translocation of ALP from the cytoplasm to the plasma membrane.…”

Changes in Expression of Connexin 32, Bile Canaliculus-Like Structures, and Localization of Alkaline Phosphatase in Primary Cultures of Fetal Rat Hepatocytes

“…On the other hand, glucocorticoids enhance Cx32 expression in primary cultured rat hepatocytes and MH 1 C 1 rat hepatoma cells [17]. Our previous study of primary cultured fetal rat hepatocytes demonstrated that dexamethasone (DEX) induces the formation of bile canaliculus-like structures (BCLS), the localization of alkaline phosphatase (ALP) in the plasma membrane around BCLS, and the expression of Cx32 along the borders between adjacent cells [6, 8, 9]. However, we have not yet demonstrated whether Cx32 expression is related to BCLS and the localization of ALP in fetal rat hepatocytes.…”