1. Post-heparin plasma that promoted rapid hydrolysis of about 90% of the triacylglycerol markedly stimulated the uptake or binding of chylomicron cholesteryl ester by suspended hepatocytes. The net hydrolysis of chyle cholesteryl ester after the uptake by the cells was, however, slower than in vivo. 2. The cholesteryl ester uptake in the presence of post-heparin plasma was larger if the cells had been preincubated for 2h. It was inhibited by the presence of colchicine, vinblastine or cycloheximide during the preincubation, and by mild trypsin treatment of the preincubated cells. 3. The results suggested that the anti-microtubular agents, but not cycloheximide, also inhibited the hydrolysis of chyle cholesteryl ester after uptake or binding to the cells. 4. The uptake of isolated chylomicron remnant particles was more efficient than that of native chyle lipoproteins. It was, however, still stimulated by heparin alone and by post-heparin plasma. The heparin-stimulated uptake was markedly decreased if cycloheximide was present during the preincubation period.
