Effect of dietary polyunsaturated phospholipid on the chemical composition of mesenteric lymph chylomicrons and the excretion of steroids into bile and feces in rat.

The effect of soybean phospholipid (SP) on the chemical composition of lymph chylomicrons and excretion of steroids into bile and feces was examined. Rats were meal-fed (9 am-10 am) or ad libitum-fed on diets containing phospholipid and neutral lipid (soybean oil or corn oil) for 2 weeks in order to assess the amount of chylomicrons secreted from the intestine during the absorption or post-absorption of dietary lipids. In meal-fed rats, dietary SP decreased the concentration of surface com-ponents (phospholipid, cholesterol and apoprotein A-I) of large chylomi-crons and increased the core components (triglyceride) of small chylomi-crons. In ad libitum-fed rats given SP, the concentration of triglyceride in small chylomicrons appeared to increase. Dietary SP increased the relative proportion of linoleic acid and decreased arachidonic acid at the 2-position of chylomicron-phospholipids. The calculated diameter of large and small chylomicron particles in meal-fed rats given SP increased and the particle number per ml lymph decreased compared to those values in rats given neutral lipid. The particle size of the small chylomicron in ad libitum-fed rats given SP also increased. Apoprotein A-I in lymph d>1.006 g/ml decreased in the SP-fed rats. The permeability of glucose-6-phosphate to microsomal membrane increased in the SP-fed rats. The excretion of neutral, but not acidic steroids into the bile and feces was increased in SP-fed rats. The results suggest that dietary SP inhibits the supply of the surface components of chylomicrons to the chylomicron precursors by interfering with absorption of the lipids in the upper part of the intestine and altering the subsequent metabolism of these lipids and apoproteins in the intestinal cells.