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Mechanisms of linoleic acid uptake by rabbit small intestinal brush border membrane vesicles
Author(s) -
Ling KitYin,
Lee HsinYi,
Hollander Daniel
Publication year - 1989
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02535264
Subject(s) - linoleic acid , chemistry , vesicle , biochemistry , fatty acid , cytosol , membrane , brush border , chromatography , biophysics , biology , enzyme
We examined the initial transport of a long‐chain unsaturated fatty acid, linoleic acid, by brush border membrane vesicles isolated from rabbit small intestine. This preparation allowed us to examine the transport of linoleic acid across the brush border membrane without the effect of the unstirred water layer or cytosol binding proteins. Linoleic acid was solubilized in a 2 mM taurocholate solution which did not compromise the functional integrity of the vesicles. Linoleic acid uptake in the range of 1 to 100 μM followed passive diffusion kinetics. Time course study showed that linoleic acid uptake reached maximal levels during the initial 15 seconds. Although the amount of linoleic acid accumulated in the vesicles diminished over the next 30 minutes, the molar quantity was still twentyfold higher than that of D‐glucose (6.5 vs 0.33 nmol/mg protein). Uptake of D‐glucose by the vesicles demonstrated typical osmotic responsiveness. We found no osmotic effect on linoleic acid uptake. Hypotonic lysis of membrane vesicles loaded with linoleic acid released 40% of the fatty acid. We concluded that a major portion of the accumulated fatty acid was bound to or incorporated into the membrane itself while ca. 40% did traverse the membrane and accumulated in the intravesicular space as nonmicellar aggregates. The known inhibitors of anion transport, diisothiocyanatostilbene and isothiocyanatostilbene did not change the transport of linoleic acid. We conclude that, in the absence of an unstirred layer or cytosol proteins, linoleic acid transport at up to 100 μM concentration is passive with rapid accumulation both by the cell membrane and the lumen of vesicles.