Changes in the activity and distribution of alkaline phosphatase (ALP) in primary cultured rat hepatocytes

Changes of the activity and localization of alkaline phosphatase (ALP) were studied in primary cultured rat hepatocytes. The activity of ALP slowly increased after isolation and reached a plateau by 48 hours. This increment was thought to have been resulted from the functional recovery after the hepatocytes regained cell to cell contact and also from the obstructive effect on the newly formed bile canaliculus under monolayer culture. The histochemical studies revealed that the localization of ALP was shifted along with the change in the direction of transcellular mobilization of materials across the hepatocyte. Addition of taurocholate and taurodeoxycholate into the culture medium resulted in enhanced activity of ALP with increased reaction products in the endoplasmic reticulum. These findings suggest that ALP has a primary role for the transportation of materials across the hepatocyte and the elevated serum level of ALP in cholestatic diseases is partly explained by the induction of ALP by bile acids which accumulate much in the serum during cholestasis.