Dietary docosahexaenoic acid affects stearic acid desaturation in spontaneously hypertensive rats

Docosahexaenoic acid (DHA, 22:6n-3) is an n-3 polyunsaturated fatty acid wh ich attenuates the development of hypertension in spontaneously hypertensiv e rats (SHR). The effects of DHA on delta-9-desaturase activity in hepatic microsomes and fatty acid composition were examined in young SHR. Two group s of SHR were fed either a DHA-enriched diet or a control diet for 6 wk. De saturase activity and fatty acid composition were determined in hepatic mic rosomes following the dietary treatments. Delta-9-desaturase activity was d ecreased by 53% in DHA-fed SHR and was accompanied by an increase in 16:0 a nd a reduction in 16:1n-7 content in hepatic microsomes. The DHA diet also increased the levels of eicosapentaenoic acid (20:5n-3) and DHA. The n-6 fa tty acid content was also affected in DHA-fed SHR as reflected by a decreas e in gamma-linolenic acid (18:3n-6), arachidonic acid (20:4n-6), adrenic ac id (22:4n-6), and docosapentaenoic acid (22:5n-6). A higher proportion of d ihomo-gamma-linolenic acid (20:3n-6) and a lower proportion of 20:4n-6 is i ndicative of impaired delta-5-desaturase activity. The alterations in fatty acid composition and metabolism may contribute to the antihypertensive eff ect of BHA previously reported.