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 3Holeate into isolated rat heart myocytes were examined. Cells were incubated at 37 degrees C with 3Holeate 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 3Holeate 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 3Holeate was selectively inhibited. These data indicate that at least a portion of myocardial fatty acid uptake is mediated by a specific membrane protein.