title: Modulation of tissue prostaglandin synthesizing capacity by increased ratios of dietary alpha-linolenic acid to linoleic acid.
abstract: Semipurified diets containing ratios of alpha-linolenic acid (18:3 omega 3) to linoleic acid (18:2 omega 6) of 1/32, 1/7, 1/1, and 3.5/1 in the form of corn oil, soybean oil, soybean/linseed oil mix and linseed oil were fed to rats for 2 months. The first 3 diets were fed to another group of rats for 4 months and to a group through the second generation. Fatty acid analysis of liver and spleen ethanolamine glycerophosphatide revealed that, as the level of 18:3 omega 3 in the diet increased, the elongated, desaturated metabolites of the omega 6 series decreased and the omega 3 series increased. Noteworthy was the depression in the amount of the precursor of the 2-series prostaglandins (PG) as the omega 3 levels increased. Synthesis of PG by liver of rats fed 2 or 4 months markedly decreased, but at 2 months in thymus and spleen, it showed a trend toward decreasing only. Brain slices showed no decrease in PGF2 alpha synthesis after 4 months, but did decrease significantly after feeding the diets to the second generation. Synthesis of PGE2 by spleen homogenate from the second generation also significantly decreased. The replacement of omega 6 series fatty acids by omega 3 series is explained by the effective competition of 18:3 omega 3 over 18:2 omega 6 for the delta 6 desaturase. Depressions in PG synthesis by high dietary 18:3 omega 3 is explained by the competitive inhibition of the PG synthetase complex by 20:5 omega 3 as well as by the decreased levels of 20:4 omega 6.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D004032:Diet; D005227:Fatty Acids / Q000032:analysis; D005260:Female; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism* / Q000494:pharmacology; D008042:Linolenic Acids / Q000378:metabolism* / Q000494:pharmacology; D008099:Liver / Q000032:analysis; D008297:Male; D011453:Prostaglandins / Q000096:biosynthesis*; D051381:Rats; D011917:Rats, Inbred Lew; D013154:Spleen / Q000378:metabolism; D013950:Thymus Gland / Q000378:metabolism; D017962:alpha-Linolenic Acid
chemical_list: D005227:Fatty Acids; D008041:Linoleic Acids; D008042:Linolenic Acids; D011453:Prostaglandins; D017962:alpha-Linolenic Acid; D019787:Linoleic Acid