Beschreibung:
AbstractSemipurified diets containing ratios of α‐linolenic acid (18∶3ω3) to linoleic acid (18∶2ω6) 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∶3ω3 in the diet increased, the elongated, desaturated metabolites of the ω6 series decreased and the ω3 series increased. Noteworthy was the depression in the amount of the precursor of the 2‐series prostaglandins (PG) as the ω3 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 PGF2α 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 ω6 series fatty acids by ω3 series is explained by the effective competition of 18∶3ω3 over 18∶2ω6 for the Δ6 desaturase. Depressions in PG synthesis by high dietary 18∶3ω3 is explained by the competitive inhibition of the PG synthetase complex by 20∶5ω3 as well as by the decreased levels of 20∶4ω6.