Alterations of secretory pattern of intestinal lipoproteins by the benzoyl ester derivative of poloxalene surfactant (BEP)

Relationship of phosphatidylcholine to hydrophobic surfactant on rat intestinal chylomicron secretion

Hydrophobic surfactants such as Poloxalene inhibit triglyceride secretion into lymph by enterocytes. The inhibitory effect of these agents on triglyceride secretion is reversed when lipid presented for absorption is exclusively in the form of phosphatidylcholine (PC) and not triglyceride. The present investigation performed in conscious mesenteric lymph fistula rats was designed to determine whether various mixtures of triglyceride and PC given intraduodenally with Poloxalene would also reverse the inhibitory effect of Poloxalene on triglyceride secretion into lymph. A 50-50 mixture of triolein (TO) and PC resulted in normal triglyceride secretion into lymph. However, when the mixture of lipids was 75-25, TO to PC, results for triglyceride recovery in lymph were considerably reduced. The transport rate for triglyceride into lymph was not as depressed, however, as observed for Poloxalene treated rats given lipid for absorption basically in the triglyceride form. Substitution of phosphatidylethanolamine for PC had no beneficial effect on triglyceride secretion in Poloxalene treated rats. It is concluded that PC can reverse the inhibitory effect of Poloxalene on triglyceride secretion into lymph even when considerable amounts of triglyceride along with PC are presented for absorption.

Carbohydrate content of apolipoprotein B-48 from rat chylomicrons of varying density

Monosaccharide composition was determined in apolipoprotein B-48 (apoB) of chylomicrons of rat mesenteric lymph. Chylomicrons were separated into three fractions based on density. Triglyceride and apolipoprotein content were determined in each. ApoB was isolated and quantified using precipitation with isopropanol. Chylomicrons were collected in lymph under normal conditions, and with Poloxalene 2930 when chylomicron secretion was inhibited. Most of the triglyceride was carried in the least dense fraction, while the highest apoB content was in the most dense fraction under normal conditions. Mannose and galactosamine contents of apoB were similar in all fractions while contents of both glucosamine and galactose were highest in the least dense fraction. When chylomicron secretion was inhibited by Poloxalene, the amount of triglyceride recovered in the least dense fraction was significantly reduced. Despite the inhibition of lipid transport in the least dense fraction of chylomicrons by Poloxalene, there was little change in apoB recoveries and in the relative content of various monosaccharides in the apoB from each of the three fractions as compared to results obtained during lipid absorption under normal conditions. In conclusion, carbohydrate composition of apoB of chylomicrons is heterogeneous and varies with chylomicron density.

Hydrophobic surfactant inhibits hypercholesterolemia in pair-fed rabbits on a cholesterol-free, low-fat diet

Poloxalene, a hydrophobic surfactant, is known to prevent hypercholesterolemia in animals fed a high-fat, high-cholesterol diet. It has not been demonstrated, however, whether this agent is of benefit when hypercholesterolemia is induced in animals by means other than the feeding of a high-fat diet. In this study, hypercholesterolemia was produced in rabbits by feeding a low-fat, cholesterol-free diet with dietary protein supplied by casein for a period of 8 weeks. Controls were given this diet without poloxalene and experimentals were given the diet with poloxalene. Total serum cholesterol levels increased in both groups, but the rise was greater for the control group. Lipoprotein analysis performed at the conclusion of the study showed significantly greater low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels in the control group as compared to the experimental group. Total protein and apolipoprotein B (apo B) were also greater in control LDL. It was concluded that poloxalene favorably affects this model of hypercholesterolemia as total serum cholesterol, LDL cholesterol, and LDL apo B were all less and the HDL cholesterol to LDL cholesterol ratio was higher in surfactant-treated rabbits.