Effect of long-chain fatty acids on the binding of thyroxine and triiodothyronine to human thyroxine-binding globulin.
The effect of long-chain fatty acids on the binding of thyroxine to highly purified human thyroxine-binding globulin has been studied by equilibrium dialysis performed at pH 7.4 and 37 degrees C. At a fixed molar ratio of 2000:1 of fatty acid to thyroxine-binding globulin, the degree of binding inhibition based on the percent change in nK value relative to the control as determined from Scatchard plots was: palmitic, 0%; stearic, 0%; oleic, 76%; linoleic, 69%; and linolenic, 61%. At a 500:1 molar ratio of oleic acid to thyroxine-binding globulin, equivalent to 0.125 mM free fatty acid in serum, thyroxine binding was inhibited by 18%, increasing to 93% at a 4500:1 molar ratio. At molar ratios of oleic acid to thyroxine-binding globulin of 1000:1, 2000:1 and 4000:1, the degree of inhibition of triiodothyronine binding was 24%, 41% and 76%, respectively. The results indicate that the unsaturated long-chain fatty acids are potent inhibitors of thyroxine binding to thyroxine-binding globulin, whereas the saturated fatty acids have little or no effect on thyroxine binding.
Tabachnick
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Korcek
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D005227:Fatty Acids / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000494:pharmacology; D008042:Linolenic Acids / Q000494:pharmacology; D008970:Molecular Weight; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000494:pharmacology; D013229:Stearic Acids / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013974:Thyroxine / Q000378:metabolism*; D013975:Thyroxine-Binding Proteins / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*; D017962:alpha-Linolenic Acid
D005227:Fatty Acids; D008041:Linoleic Acids; D008042:Linolenic Acids; D009829:Oleic Acids; D010169:Palmitic Acids; D013229:Stearic Acids; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine; D017962:alpha-Linolenic Acid; D019301:Oleic Acid; D019308:Palmitic Acid; C031183:stearic acid; D019787:Linoleic Acid; D013974:Thyroxine