Journal of Lipid Research, Vol 22, 81-94, Copyright © 1981 by Lipid Research, Inc.
New views on intestinal absorption of lipids in teleostean fishes: an ultrastructural and biochemical study in the rainbow trout
MF Sire, C Lutton and JM Vernier
Lipid absorption in rainbow trout was studied after gastric administration
of [1-14C]linoleic and [1-14C]-palmitic acids. The intestinal epithelial
cells were isolated at various times of absorption and the major lipid
classes were isolated. Radioactivity was found primarily in the
triglycerides. Blood radioactivity was measured at different times after
administration of the labeled acids. It was very low until after 6 hr.
After 4 hr when it was detectable, it was located essentially in the
triglyceride fraction. At various times after feeding (a meal with 60% of
unsaturated long chain fatty acids) the absorptive epithelium of the
anterior intestine and pyloric caeca were examined by electron microscopy.
Surprisingly, the esterification of fatty acids corresponded to the
formation of VLDL-like particles, seen in SER, RER, Golgi apparatus,
lamellar structures, intercellular space, interstitial space of lamina
propria and lumen of lymphatic vessels. The respective roles of endoplasmic
reticulum and Golgi apparatus in the lipoprotein synthesis are discussed.
The particles are delivered in the intercellular spaces by way of the
lamellar structures, whose role until now was unknown. Though the
absorption of dietary triglycerides is much slower than in mammals, the
mechanism does not differ fundamentally. The long chain fatty acids are
esterified by the intestinal cells and transferred as VLDL-like particles
to lymph. X
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