Transport of phosphatidylinositol to rat hepatocyte plasma membrane catalyzed by phosphatidylinositol transfer protein.

Plasma membrane sheets were isolated from fresh rat liver and characterized by electron microscopy and marker enzyme activities. Plasma membrane sheets were used as the acceptor membrane in the measure of transport of phosphatidyl[3H]inositol from small unilamellar phospholipid vesicles or rough endoplasmic reticulum donor membranes. Catalysis of this transport was achieved with phosphatidylinositol transfer protein purified from rat or bovine brain. Assays were designed to separate donor and acceptor membranes by density gradient centrifugation. Rates of transfer were directly proportional to incubation time and the amounts of transfer protein and plasma membrane sheet added. These results are discussed in terms of cellular phosphatidylinositol metabolism, membrane phospholipid composition, and vesicle trafficking in rat hepatocytes.