Muscle palmitate uptake and binding are saturable and inhibited by antibodies to FABP(PM).
Studies show that uptake of long-chain fatty acids (LCFA) across the plasma membranes (PM) may occur partly via a carrier-mediated process and that the plasma membrane fatty acid-binding protein (FABP(PM)) may be a component of this system. To test the hypothesis that FABP(PM) is involved in transsarcolemmal transport of LCFA in muscle, we measured palmitate uptake in giant sarcolemmal vesicles and palmitate binding to PM proteins in rat muscles, (1) in the presence of increasing amounts of unbound palmitate and (2) in the absence or presence of antibody to FABP(PM). Both palmitate uptake and binding were found to be saturable functions of the unbound palmitate concentration with calculated Vmax values of 10.5 +/- 1.2 pmol/mg protein/15 sec and 45.6 +/- 2.9 nmol/mg protein/15 min and Km values of 12.8 +/- 3.8 and 18.4 +/- 1.8 nmol/L, respectively. The Vmax values for both palmitate uptake and binding were significantly decreased by 75-79% in the presence of a polyclonal antibody to the rat hepatic FABP(PM). Antibody inhibition was found to be dose-dependent and specific to LCFA. Glucose uptake was not affected by the presence of the antibody to FABP(PM). Palmitate uptake and binding were also inhibited in the presence of trypsin and phloretin. These results support the hypothesis that transsarcolemmal LCFA transport occurs in part by a carrier-mediated process and that FABP(PM) is a component of this process in muscle.
Turcotte
L P
LP
Department of Exercise Sciences, University of Southern California, Los Angeles 90089-0652, USA.
Swenberger
J R
JR
Tucker
M Z
MZ
Yee
A J
AJ
Trump
G
G
Luiken
J J
JJ
Bonen
A
A
D000818:Animals; D000906:Antibodies / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D002352:Carrier Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D007700:Kinetics; D008099:Liver / Q000737:chemistry; D008297:Male; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010168:Palmitates / Q000378:metabolism*; D010693:Phloretin / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D012508:Sarcolemma / Q000737:chemistry / Q000378:metabolism*; D014357:Trypsin / Q000494:pharmacology
D000906:Antibodies; D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010168:Palmitates; D014357:Trypsin; D010693:Phloretin