DIETARY ESSENTIAL FATTY-ACID DEFICIENCY DIFFERENTIALLY AFFECTS TISSUES OF RATS

Quantitative Variations of polyunsaturated fatty acids (PUFA) were stu died in various tissues: red blood cells (RBC), hepatic microsomes, ki dney, skeletal muscle and heart of young rats fed either a control die t (n = 7) or an essential fatty acid (EFA)-deficient diet (n = 7). Aft er 4 wk, the EFA-[deficient rats had significantly lower proportions o f (n-6) and (n-3) fatty acids in RBC, hepatic microsomes and kidney th an the control group. Paradoxically, normal proportions of arachidonic acid [20:4(n-6)] and 5,8,11,14,17-eicosapentaenoic acid [20:5(n-3)] w ere retained in heart and skeletal muscle despite generally lower prop ortions of the precursors, 18:2(n-6) and 18:3(n-3). Morever, absolute levels of 20:4(n-6) and 20:5(n-3) in skeletal muscle of the EFA defici ent group were significantly higher than in controls and 22:5(n-3) and 22:6(n-3) levels were comparable. This suggests that fatty acid propo rtions alone, without any consideration of long-chain polyunsaturated fatty acid quantities, may not reflect the (n-6) and (n-3) PUFA status of individual tissues. This study indicates that diet-[induced change s in the PUFA composition of RBC, which are often used in clinical inv estigations, do not fully reflect the changes in the fatty acid compos ition of organs, and that individual tissues respond differently to EF A deficiency. The conservation of proportional and absolute levels of 20:5(n-3) and 20:4(n-6), and the decrease in the more unsaturated homo logues in the heart, suggest that this organ may avidly retain 20:5(n- 3) and 20:4(n-6) in order to maintain eicosanoid production.