EFFECT OF AN N-3 FATTY ACID-DEFICIENT DIET ON THE ADENOSINE-DEPENDENTMELATONIN RELEASE IN CULTURED RAT PINEAL

We studied the effect of a diet deficient in n-3 fatty acids on the ad enosine-dependent melatonin release from cultured rat pineal gland aft er stimulation by 5'-N-ethylcarboxamidoadenosine (NECA), an A2 adenosi ne agonist. Experiments were conducted with 2-month-old rats raised on semipurified diets containing either peanut oil (n-3 deficients) or p eanut plus rapeseed oil (controls). The proportion of docosahexaenoic acid (22:6 n-3) in the pineal total lipid fraction and in phosphatidyl choline and phosphatidylethanolamine was significantly decreased in n- 3-deficient rats. This was compensated for partially by an increase in 22:4 n-6 and 22:5 n-6 levels. The activity of the cultured rat pineal , in terms of cyclic AMP content and N-acetylserotonin and melatonin r elease in the medium, was lower after stimulation by 10(-5) mol/L NECA in the group fed peanut oil than in the group fed peanut plus rapesee d oil. The increased ratio of n-6/n-3 fatty acids in pineal total lipi ds and the major glycerophospholipids (phosphatidylcholine and phospha tidylethanolamine) may have an important influence on the rat pineal r esponses. The results are discussed in the context of changes in membr ane-bound proteins, including enzymes and/or receptors involved in the rat pineal gland function.