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APPETITE, OBESITY AND METABOLISM

Palmitate movement across red and white muscle membranes of rainbow trout

Departments of ¹Biology and ³Medicine, McMaster University, Hamilton, Ontario L8S 4K1; and ²of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1

Submitted 11 June 2003 ; accepted in final form 4 September 2003

We examined the movement of [³H]palmitate across giant sarcolemmal vesicles prepared from red and white muscle of rainbow trout (Oncorhynchus mykiss). Red and white muscle fatty acid carriers have similar affinities for palmitate (apparent K_m = 26 ± 6 and 33 ± 8 nM, respectively); however, red muscle has a higher maximal uptake compared with white muscle (V_max = 476 ± 41 vs. 229 ± 23 pmol·mg protein^-1·s^-1, respectively). Phloretin (250 µM) inhibited palmitate influx in red and white muscle vesicles by 40%, HgCl₂ (2.5 mM) inhibited palmitate uptake by 20-30%, and the anion-exchange inhibitor DIDS (250 µM) inhibited palmitate influx in red and white muscle vesicles by 15 and 30%, respectively. Western blot analysis of red and white muscle vesicles did not detect a mammalian-type fatty acid transporter (FAT); however, preincubation of vesicles with sulfo-N-succinimidyloleate, a specific inhibitor of FAT in rats, reduced palmitate uptake in red and white muscle vesicles by 15 and 25%, respectively. A mammalian-type plasma membrane fatty acid-binding protein was identified in trout muscle using Western blotting, but the protein differed in size between red and white muscle. At low concentrations of free palmitate (2.5 nM), addition of high concentrations (111 µM total) of oleate (18:0) caused 50% reduction in palmitate uptake by red and white muscle vesicles, but high concentrations (100 µM) of octanoate (8:0) caused no inhibition of uptake. Five days of aerobic swimming at 2 body lengths/s and 9 days of chronic cortisol elevation in vivo, both of which stimulate lipid metabolism, had no effect on the rate of palmitate movement in red or white muscle vesicles.

long-chain fatty acid; transport; rainbow trout (Oncorhynchus mykiss); sarcolemmal vesicle

This article has been cited by other articles:

				C. L. Milligan Of fish, fat, and fuel: fatty acid transport in trout muscle Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2004; 286(1): R23 - R24. [Full Text] [PDF]