The effects of season and exercise on the levels of plasma polyunsaturated fatty acids and lipoprotein cholesterol in young rats.

Plasma concentrations of polyunsaturated fatty acids (20:4(n - 6), 20:5(n - 3), 22:6(n - 3)) and high- or low-density lipoprotein cholesterols (HDL-C, LDL-C) in young rats were measured to elucidate a possible relationship between the levels of [20:5(n - 3)] [20:4(n - 6)]-1, [22:6(n - 3)] [20:4(n - 6)]-1 and [LDL-C] [HDL-C]-1. Seasonal change in [LDL-C] [HDL-C]-1 in the sedentary and exercised rats was found to correlate with the respective values of [20:5(n - 3)] [20:4(n - 6)]-1 and/or [22:6(n - 3)] [20:4(n - 6)]-1. Moderate exercise in summer decreased plasma arachidonic acid (20:4(n - 6)). With the decrement of the 20:4(n - 6) acid, the ratios of [20:5(n - 3)] [20:4(n - 6)]-1 and [22:6(n - 3)] [20:4(n - 6)]-1 increased to a greater degree. The [LDL-C] [HDL-C]-1 values in this case were inversely associated with the levels of [22:6(n - 3)] [20:4(n - 6)]-1. We therefore suggest that moderate physical training in summer protects arteries from thrombogenesis and lipid accumulation.