title: Differential responses to fasting and subsequent feeding by microsomal systems of rat liver: 6- and 9-desaturation of fatty acids.
abstract: Hepatic microsomal preparations from nonfasted, fasted, and fasted-fed rats were employed, together with cofactors, in studies of 9-desaturation of stearate-1-(14)C and 6-desaturation of linolenate-1-(14)C. Prior fasting sharply reduced 9-desaturation but did not affect 6-desaturation; feeding restored 9-desaturation. Position of desaturation was determined by permanganate-periodate oxidation and separation of the dicarboxylic acids. Feeding after fasting stimulated both desaturase systems but either dl-ethionine or actinomycin D prevented this. Dietary carbohydrate or saturated fat increased 9-desaturation and dietary protein increased 6-desaturation. Insulin treatment of nonfasted rats increased 9-desaturation but not 6-desaturation. High dietary unsaturated fat (20% safflower oil) stimulated 6-desaturation but inhibited the 9-desaturation response to feeding. The results indicate that the two desaturases are distinct and are inducible in response to different substances.
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D055598:Chemical Phenomena; D002621:Chemistry; D003609:Dactinomycin / Q000494:pharmacology; D003864:Depression, Chemical; D003998:Dicarboxylic Acids / Q000032:analysis; D004032:Diet; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D005001:Ethionine / Q000494:pharmacology; D005215:Fasting; D005224:Fats, Unsaturated; D005228:Fatty Acids, Essential / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008190:Lyases / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010504:Periodic Acid; D011196:Potassium Permanganate; D051381:Rats; D013229:Stearic Acids / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D003998:Dicarboxylic Acids; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D005224:Fats, Unsaturated; D005228:Fatty Acids, Essential; D007328:Insulin; D013229:Stearic Acids; D011196:Potassium Permanganate; D010504:Periodic Acid; D003609:Dactinomycin; D008190:Lyases; D005001:Ethionine