Despite recent advances in the composition of chylomicrons and very low density lipoproteins (VLDL), little is known concerning the importance of specific apoprotein constituents in normal and altered states of intestinal lipoprotein formation. The increasing awareness that the intestine is an active site of lipoprotein production and may contribute to the pathogenesis of various hyperlipidemias, makes an understanding of intestinal lipoprotein formation of potential importance. We therefore propose to study lymph lipoprotein formation and apoprotein synthesis during various conditions of lipid feeding to better define the importance of these apoproteins in intestinal lipoprotein formation. The mesenteric lymph fistula rat will be used for these studies. individual chylomicron and VLDL apoproteins (apo B, Group II apoproteins) will be purified from mesenteric lipoproteins and monospecific antisera developed. These antisera will be used to quantitate the apoprotein content of mesenteric lipoproteins and intestinal mucosa during conditions of high lipid feeding and cholesterol feeding. Change in chylomicron and VLDL apoprotein composition will be correlated with studies of apoprotein synthesis. These studies should provide insight into the importance of specific apoproteins in intestinal lipoprotein formation. The intracellular sites of apoprotein localization will be determined untra-structurally using monospecific antisera conjugated with electron dense markers. Using similar techniques, studies of apoprotein surface distribution in isolated, intact chylomicrons will be carried out. These studies on chylomicron structure will better define the surface organization of important chylomicron constituents. We will extend our studies on the role of microtubules in chylomicron secretion to gain a better understanding of whether these structures participate in intestinal lipid transport.