Inhibitory effect of colchicine on translocation of alkaline phosphatase to the plasma membrane concomitant to its induction in rat liver

Abstract

A single injection of colchicine (1--3 mg/kg body weight) caused a remarkable induction of hepatic alkaline phosphatase, which increased linearly in the homogenate starting at 5--6 h and reached a maximum level (14-fold of the control activity) at 20--22 h after the drug treatment. In the plasma membrane, however, the increase in specific activity and the recovery of alkaline phosphatase were greatly inhibited up to 12 h after the treatment. Such an inhibitory effect of colchicine was confirmed by a combination experiment of the drug treatment with bile duct ligation; in the plasma membrane elevation of the enzyme induced by bile duct ligation was also greatly retarded by colchicine. The subcellular distribution of the enzyme activity in livers was determined among the four groups of rats with or without bile duct ligation and/or colchicine administration taken at 8 h after each treatment. In the control and the bile duct-ligated livers, the highest specific activity was observed in the plasma membrane fraction, while in the colchicine-treated livers, with or without bile duct ligation, the highest activity was found in the Golgi fractions. These results indicate that the Golgi membranes enriched with the induced enzyme were blocked by the drug to prevent migration toward the plasma membranes enriched with the induced enzyme were blocked by the drug to prevent migration toward the plasma membrane, thus demonstrating involvement of the Golgi complex in the translocation route of newly synthesized alklaine phosphatase to the plasma membrane.