Very Low Density Lipoproteins in Intestinal Lymph: Origin, Composition, and Role in Lipid Transport in the Fasting State

the lipoproteins of mesenteric lymph was studied in fasting rats with mesenteric lymph fistulas. The lymph was found to contain, in addition to chylomicrons (Sf> 400), a significant amount of another, more dense, tri-glyceride-rich fraction, the very low density lipopro-teins (VLDL), which showed a peak Sf of 102. The VLDL differed from chylomicrons not only in flotation, but also in per cent lipid composition and electrophoretic mobility in agarose gel. The VLDL fraction was found to contain 47 % of the triglyceride and 54 % of the cho-lesterol of fasting lymph and, in the fasting state, was the major lipoprotein species present. When cholestyramine resin was administered intra-duodenally, or bile flow was acutely diverted from the intestine, it was demonstrated that the lipids in lymph VLDL, like those in chylomicrons, were derived from the intestine and bile. These data indicate that the VLDL in intestinal lymph are not derived from the plasma but are of intestinal origin. Because certain properties of lymph VLDL were simi-lar to those reported for plasma VLDL (per cent lipid composition, flotation coefficient, and continuing entry into plasma in the fasting state), additional compari-sons between these fractions were made. Although lymph VLDL moved to the as region in agarose gel, when they were mixed with VLDL-free serum immedi-ately before electrophoresis they showed the a, mobility of rat serum VLDL. Furthermore, immunoelectropho-retic comparison of partially delipidated lymph and se-rum VLDL revealed that these fractions shared in These studies were presented in part at the annual meetin