DETERMINANTS OF TRIACYLGLYCEROL TRANSPORT FROM THE ENDOPLASMIC-RETICULUM TO THE GOLGI IN INTESTINE

The ability of the intestinal cell to export triacylglycerol (TG) is a physiologically regulatable function. The intracellular site where th is occurs is un]mown, although available evidence suggests that the st ep between the endoplasmic reticulum (ER) and the Golgi is the most li kely. We studied this process in rat enterocytes that were isolated fr om the proximal intestine. A novel system was developed in which [H-3] TG was transported from ER to the Golgi. This process was time, ATP, t emperature, and cytosol dependent. The cytosolic factor(s) was heat an d trypsin sensitive. TG transport was directly proportional to the amo unt of added nonradiolabeled acceptor Golgi. The rate of TG transporte d to tile Golgi was the fastest in cells isolated from rats that had b een intraduodenally infused in vivo with glyceryltrioleate (TO) plus p hosphatidylcholine and slowest in cells isolated from bile-fistulated rats infused with TO in vivo compared with cells from in vivo TO-infus ed, bile duct intact rats, mimicking the relative transport rates seen in vivo. TG transport in vitro could not be quenched by adding TG emu lsions, chylomicrons, liposomes, or guanosine 5'-O-(3-thiotriphosphate ). Cytosol from the liver and kidney supported TG transport, but; the Golgi from liver or kidney did not accept TG from intestinal ER. We co nclude that an intestinally specific, active transport mechanism trans ports TG from the ER to the Golgi and that this might be a regulatory step in TG export from the intestinal cell.