The rate and extent of modification of fatty acid composition of mice lung and kidney by dietary menhaden oil (MO) was investigated. White mice were fed 2 wt% safflower oil and either 10 wt% MO or 10 wt% hydrogenated coconut oil (HCO) for 23 d. The stability of dietary MO-induced fatty acid modifications was assessed by replacing the MO diet of a group of mice after 23 d with the HCO diet for an additional 10 d. Mice were sacrificed on d 0, 1, 3, 5, 7, 14, 23 and 33. The n-3 polyunsaturated fatty acid (PUFA), 20:5n-3 and 22:6n-3 were rapidly incorporated into lung and kidney phosphoglyceride (PL) classes during the first 7 d of MO ingestion relative to the controls. After 1 wk of MO consumption, the rate of incorporation either plateaued at an elevated level or continued to increase at a much more gradual rate. A marked increase in the content of 22:5n-3 in lung and kidney was observed. A concomitant and rapid decrease was observed in the n-6 PUFA, 20:4n-6, 22:5n-6 and 18:2n-6. The minimum content of 20:4n-6 was reached between 1 and 2 wk, whereas the minimum levels of 18:2n-6 and 22:5n-6 occurred within 72 h. The n-6/n-3 PUFA ratio in lung and kidney and PL classes increased in mice fed HCO and decreased in mice fed dietary MO. When dietary MO was removed, the n-3 PUFA levels decreased with a concomitant increase in n-6 PUFA after 10 d of HCO consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

The efficacy of individual omega-3 polyunsaturated fatty acids (PUFA) in altering eicosanoid synthesis in peritoneal macrophages was studied by feeding mice for 10 days a diet containing 2 wt % fat, which included 0.5 wt % ethyl esters of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or linolenic acid (LNA). Upon stimulation with calcium ionophore A23187, macrophages from these animals produced significantly lower amounts of leukotriene C4, leukotriene B4 and 12-hydroxyeicosatetraenoic acid, prostaglandin E2 and 6-keto prostaglandin F1 alpha compared with those obtained from animals on the diets containing olive oil or safflower oil. The decrease in leukotriene synthesis was similar in the animals fed DHA, EPA or LNA diets. This depression of eicosanoids by DHA and EPA was associated with decreased levels of arachidonic acid (AA); however, LA that altered eicosanoids did not have the same effect on AA levels.

The efficacy of docosahexaenoic acid (DHA) in suppressing eicosanoid synthesis by peritoneal macrophages in vivo was influenced by the relative amount of dietary DHA when linoleic acid (LA) was held constant. Increasing DHA from 0 to 37% of the fatty acids in diets containing 10 weight % fat (of which LA was 40%) caused an eleven-fold increase in the DHA content of macrophages. Limited retroconversion of DHA to eicosapentaenoic acid was observed. Macrophages in animals consuming DHA synthesized significantly lower amounts of leukotriene E4, prostaglandin E2 and 6-keto prostaglandin F1 alpha in vivo upon stimulation with zymosan. The maximum inhibition of eicosanoid synthesis was observed when the dietary DHA/LA ratio was 0.16 and no further inhibition occurred when the ratio was increased up to 0.81.

The effects of dietary n-3 and n-6 polyunsaturated fatty acids on the fatty acid composition of phospholipid, Ca++. Mg++ ATPase and Ca++ transport activities of mouse sarcoplasmic reticulum were investigated. Mice were fed a 2 weight percent fat diet containing either 0.5 weight percent ethyl esters of 18:3n-3, 20:5n-3 or 22:6n-3 as a source of n-3 polyunsaturated fatty acid or 0.5 weight percent safflower oil as a source of n-6 polyunsaturated fatty acid for 10 days. Olive oil (2 weight percent) was used as a control diet. Although feeding n-6 polyunsaturated fatty acid induced very little modifications of the phospholipid sarcoplasmic reticulum fatty acid composition, feeding n-3 polyunsaturated fatty acid altered it markedly. Inclusion of 18:3n-3, 20:5n-3 or 22:6n-3 in the diet caused an accumulation of 22:6n-3, which replaced 20:4n-6 and 18:2n-6 in phospholipid sarcoplasmic reticulum. The saturated fatty acids were significantly increased with a concurrent reduction of 18:1n-9. These changes in the fatty acid composition resulted in a decrease in the values of the n-6/n-3 polyunsaturated fatty acid ratio and a decrease in the ratio of 20 carbon to 22 carbon fatty acids esterified in the phospholipid sarcoplasmic reticulum. This was associated with a decrease in Ca++ uptake by n-3 polyunsaturated fatty acid enriched sarcoplasmic reticulum vesicles as compared with n-6 fatty acid and control diet sarcoplasmic reticulum vesicles. However, neither the affinity for Ca++ nor the maximal velocity of ATP hydrolysis activity of Ca++.MG++ATPase were altered by the different diets.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract