Effect of linoleic acid metabolites on Na(+)/K(+) pump current in N20.1 oligodendrocytes: role of membrane fluidity.
Metabolic derivatives of linoleic acid, both monoepoxides and diols, have been reported to be toxic in humans and multiple animal tissue preparations. A previous electrophysiological study has shown these compounds produce multiple effects on the electrical activity of rat ventricular myocytes. The hydrophobic nature of these compounds suggests the possibility that these effects may be due to nonspecific lipid interactions, i.e., changes in membrane fluidity. This study investigates membrane fluidity as a possible mechanism by which linoleic acid metabolites inhibit Na(+)/K(+) pump current (I(p)). This study showed that positional isomers 9,10- and 12,13-epoxy-octadecenoic acid (EOA) and 9,10- and 12,13-dihydroxy-OA (DHOA) inhibit I(p) in a dose-dependent manner in N20.1 mouse oligodendrocytes, with greater inhibition produced by EOAs. These compounds, at 10 microM, inhibited I(p) by 4.7 +/- 1.6, 18.2 +/- 0.5, 11.7 +/- 0.5, and 25.1 +/- 0.9% for 12,13-DHOA, 9,10-DHOA, 12,13-EOA, and 9,10-EOA, respectively, in oligodendrocytes. Fluorescence recovery after photobleaching measurements showed that both DHOA isomers produced a 7-8% increase in diffusion coefficient of the probe at 10 microM, whereas the diffusion coefficient was decreased by 5 and 13% by 9,10-EOA and 12,13-EOA, respectively. There was no apparent correlation between membrane fluidity and inhibition of I(p) by these four linoleic acid metabolites. These results indicate that membrane fluidity alone cannot explain the effects of these compounds on I(p) and suggest that they have a specific interaction with the Na(+)/K(+) pump.
Ha
Joomi
J
Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, 4301 West Markham Street, Litte Rock, Arkansas 72205, USA.
Dobretsov
Maxim
M
Kurten
Richard C
RC
Grant
David F
DF
Stimers
Joseph R
JR
D000818:Animals; D005456:Fluorescent Dyes / Q000737:chemistry; D019787:Linoleic Acid / Q000378:metabolism* / Q000633:toxicity*; D008041:Linoleic Acids / Q000378:metabolism / Q000633:toxicity; D008560:Membrane Fluidity / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D009829:Oleic Acids / Q000378:metabolism / Q000633:toxicity; D009836:Oligodendroglia / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects* / Q000378:metabolism; D013050:Spectrometry, Fluorescence
C425204:12,13-dihydroxyoctadecenoic acid; C119104:12,13-epoxy-9-octadecenoic acid; D005456:Fluorescent Dyes; D008041:Linoleic Acids; D009829:Oleic Acids; C051208:9,10-epoxy-12-octadecenoic acid; D019787:Linoleic Acid; D000254:Sodium-Potassium-Exchanging ATPase