A dual, concentration-dependent absorption mechanism of linoleic acid by rat jejunum in vitro.

Linoleic acid absorption was studied using everted rat jejunal sacs. At low concentrations (42-1260 microM), the relationship between linoleic acid concentration and its absorption rate fitted best to a rectangular hyperbola. At high concentrations (2.5-4.2 mM) the relationship between the two parameters was linear. The separate additions of 2,4-dinitrophenol, cyanide, or azide, or decrease in the incubation temperature from 37 to 20 degrees C did not change the absorption rate of linoleic acid. Absorption rate of linoleic acid at low concentrations increased as the hydrogen ion and taurocholate concentrations were increased or as the unstirred water layer thickness was decreased. Linoleic acid absorption rate was decreased after the additions of lecithin, oleic, linolenic, and arachidonic acids or the substitution of taurocholate with the nonionic surfactant Pluronic F 68. These observations indicate that a concentration-dependent, dual mechanism of transport is operative in linoleic acid absorption. Facilitated diffusion is the predominant mechanism of absorption at low concentrations, while at high concentrations, simple diffusion is predominant. At low concentrations, the absorption rate of linoleic acid is influenced by the pH, surfactant type and concentration, the simultaneous presence of other polyunsaturated fatty acids, and the thickness of the unstirred water layer.

[1]  D. Small,et al.  Micelle formation by bile salts. Physical-chemical and thermodynamic considerations. , 1972, Archives of internal medicine.

[2]  A. Vergroesen.  The Role of fats in human nutrition , 1975 .

[3]  A. J. Raymond,et al.  Micelle formation of polyoxyethylene-polyoxypropylene surfactants , 1965 .

[4]  T. Csáky,et al.  Extracellular space in the epithelium of rats' small intestine. , 1974, The American journal of physiology.

[5]  A. Vergroesen.  Physiological effects of dietary linoleic acid. , 2009, Nutrition reviews.

[6]  E. Hendry.  Osmolarity of human serum and of chemical solutions of biologic importance. , 1961, Clinical chemistry.

[7]  J. Gregg.  New solvent systems for thin-layer chromatography of bile acids. , 1966, Journal of lipid research.

[8]  D. S. Riggs,et al.  A COMPARISON OF ESTIMATES OF MICHAELIS-MENTEN KINETIC CONSTANTS FROM VARIOUS LINEAR TRANSFORMATIONS. , 1965, The Journal of biological chemistry.

[9]  D. Nugteren,et al.  Enzymatic Conversion of All-cis-Polyunsaturated Fatty Acids into Prostaglandins , 1964, Nature.

[10]  R. Ockner,et al.  Fatty acid-binding protein in small intestine. Identification, isolation, and evidence for its role in cellular fatty acid transport. , 1974, The Journal of clinical investigation.

[11]  J. Dietschy,et al.  The intestinal unstirred layer: its surface area and effect on active transport kinetics. , 1974, Biochimica et biophysica acta.

[12]  N. Draper,et al.  Applied Regression Analysis , 1966 .

[13]  D. Winne.  Unstirred layer, source of biased Michaelis constant in membrane transport. , 1973, Biochimica et biophysica acta.

[14]  J. Dietschy.  Difficulties in determining valid rate constants for transport and metabolic processes. , 1970, Gastroenterology.

[15]  S. Schenker,et al.  Thiamine transport across the rat intestine. I. Normal characteristics. , 1975, Gastroenterology.

[16]  D. Hollander,et al.  Vitamin K1 intestinal absorption in vivo: influence of luminal contents on transport. , 1977, The American journal of physiology.

[17]  W. Simmonds.  Uptake of Fatty Acid and Monoglyceride , 1976 .

[18]  P. Subbaiah,et al.  Absorption of lipids. , 1972, Biochemical Journal.

[19]  H. Mekhjian,et al.  Bile Acids and the Intestinal Absorption of Fat and Electrolytes in Health and Disease , 1973 .

[20]  R. Ockner,et al.  A Binding Protein for Fatty Acids in Cytosol of Intestinal Mucosa, Liver, Myocardium, and Other Tissues , 1972, Science.