Effect of essential fatty acid depletion on tissue phospholipid fatty acids in spontaneously hypertensive and normotensive rats.

Weanling male spontaneously hypertensive (SHR) and normotensive (WKY) rats were maintained on a fat-free semisynthetic diet and killed at various intervals. The effects of fat-depletion on the appearance of essential fatty acid (EFA) deficiency symptoms, the progressive changes of major fatty acids in plasma, liver, heart, and kidney phospholipids (PL), and in skin total lipids were compared between these two strains. After five weeks on the diet, the slower growth and the appearance of EFA deficiency symptoms became evident in SHR. In general, fat-depletion reduced the levels of n-6 fatty acids, whereas it increased those of 20:3n-9. However, the fat-depletion induced reduction of 18:2n-6 in heart PL and 20:4n-6 in kidney, while the elevation of 20:3n-9 in plasma, heart, and kidney PL were greater in WKY than in SHR. As a result, the elevation of biochemical EFA deficiency index--20:3n-9/20:4n-6 ratio--was greater in WKY than in SHR. In comparison with WKY, the concentrations of liver triacylglycerols and the weights of adipose tissues in SHR were reduced to a greater extent, indicating an active catabolism of triacylglycerols in SHR. This study suggests that the earlier appearance of morphological symptoms of EFA deficiency in SHR was not associated with the reducing n-6 EFA levels or with an elevation of triene/tetraene ratio, but possibly to a reduced supply of n-6 EFA for skin prostaglandin synthesis.