Fatty acid uptake by isolated rat heart myocytes represents a carrier-mediated transport process.
The mechanism by which fatty acids enter cardiomyocytes is unclear. Therefore, the influx kinetics of [3H]oleate into isolated rat heart myocytes were examined. Cells were incubated at 37 degrees C with [3H]oleate bound to albumin in various molar ratios and the initial rate of uptake (V0) was determined as a function of the unbound oleate concentration in the medium. V0 was saturable with increasing oleate concentrations incubated (Km 78 nM; Vmax 1.9 nmol X min-1 per 10(6) cells) and temperature dependent with an optimum at 37 degrees C. Furthermore, binding of [3H]oleate to isolated plasma membranes of cardiomyocytes was saturable, revealing a KD of 42 nM, and was inhibited by heat denaturation or trypsin pretreatment of the membranes. From these membranes a single 40-kD protein with high affinity for a variety of long chain fatty acids was isolated. With a monospecific antibody to this membrane protein, binding as well as cellular influx of [3H]oleate was selectively inhibited. These data indicate that at least a portion of myocardial fatty acid uptake is mediated by a specific membrane protein.
Stremmel
W
W
Department of Medicine, University Clinics of Düsseldorf, Federal Republic of Germany.
D000418:Albumins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000302:isolation & purification / Q000502:physiology*; D002463:Cell Membrane Permeability; D002469:Cell Separation; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000032:analysis; D013347:Subcellular Fractions / Q000378:metabolism
D000418:Albumins; D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009829:Oleic Acids; D019301:Oleic Acid