Size of Lipoprotein Particles in the Intestinal Lymph of Rats Fed on Corn Oil, Peanut Oil, Rapeseed Oil or Canbra Oil

Abstract

The release of chylomicrons (d > 0.1 µm) and very low density lipoprotein-like particles (d ≤ 0.1 µm) by the intestinal mucosa of rats was followed by means of electron microscopy of the intestinal lymph after ingestion of four oils: corn and peanut oils, both containing large amounts of C18 unsaturated fatty acids (85 and 82%, respectively), especially linoleic acid (50%) in the corn oil and oleic acid (53%) in the peanut oil, and two crucifer oils: rapeseed oil, with a high erucic content (53%) and canbra oil with alow erucic content but rich in oleic acid (62%). The absorption of rapeseed oil took place at a very early stage and was very rapid; practically within the first 6 h. The absorption of corn oil also began early but it took longer. As for canbra and peanut oils, their absorption occurred later and evolved in the same manner but with, however, greater rapidity for the canbra oil. The proportion of chylomicrons observed in lymph following the ingestion of canbra oil, especially those larger than 0.2 µm, was higher than the proportion observed after ingestion of peanut oil, but the release of chylomicrons during the course of absorption of either oil followed the same evolution. Most of the fatty acids of these two oils were thus transported by chylomicrons, especially after ingestion of canbra oil. A delayed release of chylomicrons occurred after the ingestion of rapeseed oil. Since the absorption of this oil began very early and increased rapidly, most of the fatty acids, particularly erucic acid, were carried in small chylomicrons and by very low density lipoprotein (VLDL)-like particles. The large proportion and the rapidity of the release of chylomicrons after ingestion of peanut oil and particularly canbra oil could be ascribed to the oleic acid content of these two oils. The results concerning the absorption of rapeseed oil could be explained by the saturated character of erucic acid. The incorporation of large amounts of this acid in the smaller lipoprotein particles of lymph could partly explain the abnormal metabolism of erucic acid in the tissues, especially in the myocardium, different from that observed for oleic acid in canbra oil, which is mainly transported in chylomicrons.