Metabolism of deuterium-labeled linoleic, 6,9,12-octadecatrienoic, 8,11,14-eicosatrienoic, and arachidonic acids in the rat.
Male weanling rats were fed a diet that contained 2.1% ethyl oleate, 1% ethyl linoleate, and 0.2% ethyl linolenate. After 4 weeks all the linoleate was replaced by the deuterium-labeled analog and the animals were killed 4 days later. The molar fraction of total 20:4(n-6) in liver, heart, and kidney phospholipids containing deuterium was 33.9, 8.9, and 13.3%, respectively. Second, animals were preconditioned by incorporating either 0.2% of 18:3(n-6), 20:3(n-6), or 20:4(n-6) into the above diet and again after 4 weeks all the linoleate was replaced with the labeled analog. Now the molar fraction of labeled 20:4(n-6) in liver phospholipids from these three groups of animals was reduced from 33.9 to 27.1, 23.9, and 24.1% respectively. In contrast, there was little change in the specific activity of 20:4(n-6) in heart and kidney phospholipids. The third protocol was a direct crossover study in that again unlabeled linoleate was fed during the entire period. Four days prior to killing the unlabeled 18:3(n-6), 20:3(n-6), and 20:4(n-6) were replaced with the deuterium-labeled analogs. The mole % of total esterified 20:4(n-6) in liver phospholipids was now 24.6, 32.0, and 26.2%, respectively. Even though 18:3(n-6), 20:3(n-6), and 20:4(n-6) were all fed at only 20% of the level of 18:2(n-6), it can be calculated that the molar fraction of esterified 20:4(n-6) in liver phospholipids was between 65 to 77% of that found when 18:2(n-6) was the only dietary (n-6) acid as under these conditions 33.9 mol % of the 20:4(n-6) was labeled. Interestingly, when deuterium-labeled 18:3(n-6), 20:3(n-6), or 20:4(n-6) was fed, the specific activity of esterified 20:4(n-6) in kidney and heart phospholipids was always equal to or greater than what was derived from deuterium-labeled 18:2(n-6). The results show that under steady-state dietary conditions, (n-6) dietary fatty acids are processed in different ways by liver, heart, and kidney.
Luthria
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Department of Medical Biochemistry, Ohio State University, Columbus 43210, USA.
Sprecher
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D015126:8,11,14-Eicosatrienoic Acid / Q000378:metabolism*; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003903:Deuterium; D004951:Esterification; D007668:Kidney / Q000378:metabolism; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017965:gamma-Linolenic Acid / Q000378:metabolism*
D008041:Linoleic Acids; D010743:Phospholipids; D016718:Arachidonic Acid; D017965:gamma-Linolenic Acid; D019787:Linoleic Acid; D003903:Deuterium; D015126:8,11,14-Eicosatrienoic Acid