SHORT-TERM EFFECTS OF DIETARY FATS ON THE LIPID-COMPOSITION AND DESATURASE ACTIVITIES OF RAT-LIVER MICROSOMES

Diets supplemented with 10% coconut, olive or sunflower oil were given to rats at weaning. After two, four and six days, the lipid compositi on and desaturase activities of liver microsomes were measured. The pe rcentage of oleic acid and Delta(9)-desaturase activity were increased in animals fed an olive oil diet while animals given sunflower oil sh owed the highest content of linoleic and polyunsaturated n-6 fatty aci ds. On day 6, olive oil-fed rats had the highest levels of 22:6 n-3 in the phosphatidylethanolamine fraction. Saturated fatty acids were sim ilar among dietary groups, despite the marked differences in the satur ated fatty acid content of the three oils. Polyunsaturated n-6 and n-3 fatty acids decreased during the six days of feeding with coconut oil . Our results show that liver microsome membranes respond to different dietary fatty acids sources by changes in enzyme activities and relat ive content of some fatty acids after a period of dietary manipulation as brief as 6 days.