Studies of regulation of free fatty acid (FFA) utilization by skeletal muscles have focused on plasma FFA delivery and on intracellular factors affecting FFA metabolism. The present study was conducted to directly analyse the uptake process of fatty acids into single myocytes. Cells were isolated from the rat flexor digitorum brevis muscle. Confocal laser scanning microscopy was utilized to analyse the uptake of the fluorescent fatty acid derivative 12-NBD-stearate, which is not metabolized by muscle tissue. Uptake represented a saturable function of the unbound fatty acid concentration in the medium (K(m) 366 +/- 118 nM, Vmax 2.1 +/- 0.3 AU/s) and depended on the medium sodium concentration. Reduced buffer pH increased initial uptake rates, whereas lactate (10 mM) had no effect. Membrane hyper- and depolarization decreased uptake rates. This study demonstrates for the first time kinetic data from isolated myocytes with evidence for a carrier-mediated transport mechanism for long-chain fatty acids.

1991organo-boron compounds, nonmetal heterocycles organo-boron compounds, nonmetal heterocycles S 0047 -196Twofold Borylation of Benzene Derivatives with (Diisoalkylamino) boradiyl Units.-Reaction of the benzene derivatives (I) and (IV) with the difluoroboranes (II) and (V), resp., according to A) causes defluorination to give the diborabicyclooctadienes (III) and (VI). In contrast, the reaction of (IV) with (II) affords the boroloborole (VII) . An analogous product was previously reported from the reaction of benzene with (II). -(MELLER, A.; BOEKER, C.; SEEBOLD, U.; BROMM, D.; MARINGGELE, W.; HEINE, A.; HERBST-IRMER, R.; POHL, E.; STALKE, D.; NOLTEMEYER, M.; SHELDRICK, G. M.; Chem.