MODULATION OF NOREPINEPHRINE-STIMULATED CYCLIC-AMP ACCUMULATION IN RAT PINEALOCYTES BY N-3 FATTY-ACIDS

This work showed that docosahexaenoic (22:6n-3) and eicosapentaenoic ( 20:5n-3) acid supplementation for 48 h have opposite effects on the no repinephrine-stimulated cyclic AMP accumulation in rat pinealocytes. W e found that 22:6n-3 supplementation of pineal cells, done by increasi ng specifically 22:6n-3 in phospholipid and triacylglycerol pools, led to inhibition of norepinephrine-stimulated cyclic AMP production wher eas 20:5n-3 supplementation, by increasing 20:5n-3, 22:5n-3 and 22:6n- 3 in the same pools, stimulated it. In contrast, direct treatment of p inealocytes with each fatty acid (50 mu M) did not affect cyclic AMP p roduction in the presence of (0.1-10 mu M) norepinephrine. The results indicate that, using pharmacological agents such as forskolin or praz osin: (a) neither basal nor forskolin-stimulated cyclic AMP levels wer e modified in fatty acid-supplemented cells compared to control cells; (b) in the presence of 1 mu M prazosin, the activation by 20:5n-3 was still effective whereas no additional inhibition of norepinephrine st imulation was observed in 22:6n-3-supplemented cells. Taken together, our results suggest that 22:6n-3 or 20:5n-3 supplementation modulates specifically the alpha(1), or beta-adrenoceptors in the rat pineal gla nd.