Long-term saturated fat supplementation in the rat causes an increase in PGI2/TXB2 ratio of platelet and vessel wall compared to n-3 and n-6 dietary fatty acids.

The effect of long-term manipulation of dietary lipid intake on platelet and vessel wall lipid composition and eicosanoid synthesis was investigated. Rats were fed a standard diet (REF diet) supplemented (12% w/w) with either sheep fat (SF), sunflower seed oil (SSO) or tuna fish oil (TFO) for a period of 15 months. Significant compositional changes both in the aorta and platelets were observed following dietary lipid treatment and differences between these tissues were particularly apparent with regard to the incorporation and conversion of n-3 fatty acids. For example, platelets displayed a selective accumulation of eicosapentaenoic acid (EPA, 20:5 n-3) over docosahexaenoic acid (DHA, 22:6, n-3), but in the aorta the proportion of DHA was considerably higher than that of EPA. In both tissues, compared to REF diet, n-3 dietary fatty acids replaced the n-6 unsaturates 20:4 and 22:4, but did not affect the proportion of linoleic acid. In contrast to aorta, the unsaturation index for platelet membrane varied significantly between dietary groups. The capacity of aorta and platelets to generate PGI2-like activity and thromboxane was unaltered by the SSO diet. However, changes were seen following SF and TFO supplementation. Rats fed the SF diet displayed a greater synthetic capacity whilst in animals maintained on TFO diet the synthesis of these two eicosanoids was considerably suppressed. The SF group displayed the highest value for PGI2/TXB2 ratio whereas TFO diet fed rats showed the lowest which may partly be due to synthesis of TXA3. The reduction in eicosanoids following the tuna fish oil supplementation can be explained on the basis of concurrent compositional changes.(ABSTRACT TRUNCATED AT 250 WORDS)