Differential secretion of α1-acid glycoprotein occurs in the Golgi complex of isolated rat hepatocytes.

Using weakly basic amines, we investigated the step at which the secretion kinetics of concanavalin-A-retained and nonretained αl-acid glycoprotein glycoforms diverge in isolated rat hepatocytes. Both chloroquine and primaquine, whose action on protein secretion is targeted to terminal domains of the Golgi apparatus, cancelled the kinetic difference without influencing carbohydrate chain sialylation. To test for a possible interaction of al-acid glycoprotein with Golgi membranes, we also permeabilized control and primaquine-treated hepatocytes, as well as purified Golgi preparations, with saponin. In each case, we found that al-acid glycoprotein was associated with Golgi membranes, the association being more marked in primaquine-treated cells than in control cells. Membrane-bound al-acid glycoprotein appeared to be preferentially retained on concanavalin A. Such retention could account for the divergent secretion kinetics of al-acid glycoprotein glycoforms. [ABSTRACT FROM AUTHOR]