a1 Nutritional Biochemistry Unit, The Institute of Zoology, Regent's Park, London NWl 4RY
1. The oxidation rates of lauric, myristic, palmitic, stearic, oleic, α-linolenic, linoleic, γ-linolenic, dihomo- γ-linolenic and arachidonic acids were studied by use of a radioisotope tracer technique in weanling rats at rest in a metabolism chamber over 24 h.
2. Of the saturated fatty acids, lauric acid (12:O) was the most efficient energy substrate: the longer the chain length of the saturated fatty acids, the slower the rate of oxidation.
3. Oleic acid (18:1) was oxidized at a remarkably fast rate, similar to that of lauric acid.
4. Of the ω6 essential fatty acids studied, linoleic acid (18:2ω6) was oxidized at a faster rate than any of its metabolites, with arachidonic acid (20:4ω6) being oxidized at the slowest rate.
5. The rate of oxidation of γ-linolenic acid (18:3ω3) was almost as fast as that of lauric and oleic acids.
(Received June 25 1986)
(Accepted November 25 1986)