Biochemical and electron microscope radioautographic study of intestinal absorption of tritiated palmitic and oleic acids in control and actidione-cycloheximide-treated rats.
Intestinal absorption of tritiated palmitic and oleic acids was investigated in control and actidione-cycloheximide-treated rats. Pancreatic juice was collected and 24 hr later an intestinal loop was cannulated in situ. A 90 mumole-lipid emulsion composed of an equimolar mixture of monopalmitin, palmitic and oleic acids with bile was infused with either 3H-labeled palmitic or oleic acid. After 15 or 30 min biochemical analysis was carried out to follow the uptake and the transfer of the labeled fatty acids. Mucosa was removed for both biochemical analysis of lipid classes and the ultrastructural or radioautographic electron microscope study depending on the radioactive activity. Following actidione-cycloheximide treatment, the uptake of both fatty acids decreased, but the amount of lipids in the mucosa greatly increased, while amount of the reesterification of fatty acids in the mucosa diminished. Consequently the amount of infused palmitic acid which was transferred in 15 min decreased from 36% in the absence of treatment to 4.6% when treatment was used. The corresponding figures for oleic acid are 70% and 20.9%. Unstructured lipids were in the intercellular spaces, indicating that a cytotoxic effect had occurred which produced a defect in the lipoprotein particle organization. The Golgi complex, in the final step of the chylomicron synthesis before exocytosis, showed low level of radioautographic reaction indicating less participation by the complex in lipid transfer. The various processes which were inhibited during long-chain fatty acid absorption from the luminal area to the Golgi complex included fatty acid binding by proteins, enzymatic acylation and esterification, apoprotein participation. This inhibition explains why long-chain fatty acid absorption was greatly impaired. Moreover, our observations compared with those obtained during decanoic acid absorption, particularly our radioautography based observations, emphasize the important role of the Golgi complex which requires intense membrane turnover during lipid absorption.
D000818:Animals; D001345:Autoradiography; D003513:Cycloheximide / Q000494:pharmacology*; D004951:Esterification; D006056:Golgi Apparatus / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000378:metabolism / Q000648:ultrastructure; D050356:Lipid Metabolism; D008854:Microscopy, Electron; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D051381:Rats; D014316:Tritium
D009829:Oleic Acids; D010169:Palmitic Acids; D014316:Tritium; D019301:Oleic Acid; D019308:Palmitic Acid; D003513:Cycloheximide