title: A study of the effect of alpha-linolenic acid on the desaturation of dihomo-gamma-linolenic acid using rat liver homogenates.
abstract: The effects of alpha-linolenic acid on delta 5 desaturation of 20: 3 n-6 dihomo-gamma-linolenic acid) to 20: 4 n-6 (arachidonic acid) and on delta 6 desaturation of 18: 2 n-6 (linoleic acid) to 18:3 n-6 (gamma-linolenic acid) were investigated in two different studies using rat liver homogenates. In the first study, rats were fed a semi-synthetic fat-free diet. When unlabelled 18:3 n-3 was added to the incubation of 14C 18:2 or 14C 20:3, the desaturation rates decreased. delta 6 Desaturation was more strongly inhibited than delta 5 desaturation. The position isomer, gamma-linolenic acid, had no significant effect on delta 6 and delta 5 desaturation. In the second study, the rats were fed a diet including alpha-linolenic acid in the form of rapeseed oil containing no erucic acid. The control animals were fed a peanut oil diet. When alpha-linolenic-fed rats were compared to control animals, we found that delta 6 desaturase activity was lower in the alpha-linolenic-fed animals. In contrast, there was no significant effect on the desaturation rate when 14C 20:3 n-6 was used as a substrate. Our results lead to the conclusion that alpha-linolenic acid, when given to rats as dietary rapeseed oil, partly inhibited delta 6 desaturation in vitro, but did not affect significantly subsequent delta 5 desaturation in the biosynthesis of arachidonic acid. The inhibition of the delta 5 desaturation step, when alpha-linolenic acid was added to the incubation, might be due to an unknown competitive mechanism. These observations have been discussed in relation with the current literature.
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000096:biosynthesis; D010367:Arachis; D001937:Brassica; D000090943:Delta-5 Fatty Acid Desaturase; D004041:Dietary Fats / Q000008:administration & dosage; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism; D008042:Linolenic Acids / Q000008:administration & dosage* / Q000378:metabolism; D050602:Linoleoyl-CoA Desaturase; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D017962:alpha-Linolenic Acid
chemical_list: D001095:Arachidonic Acids; D000090943:Delta-5 Fatty Acid Desaturase; D004041:Dietary Fats; D005231:Fatty Acids, Unsaturated; D008041:Linoleic Acids; D008042:Linolenic Acids; D017962:alpha-Linolenic Acid; D016718:Arachidonic Acid; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase; D015126:8,11,14-Eicosatrienoic Acid