POLYUNSATURATED FATTY-ACIDS IN CULTURED CARDIOMYOCYTES - EFFECT ON PHYSIOLOGY AND BETA-ADRENOCEPTOR FUNCTION

This study was carried out to investigate the influence of the membrane fatty acid composition on the basal electrical and contractile activities and the response to beta-adrenergic stimulation of rat cardiac muscle cells in culture. Cells were grown for 3 days in a conventional serum culture medium and then incubated for 24 h in synthetic media containing either n-6 or n-3 as the sole source of polyunsaturated fatty acids (PUFA). The n-6/n-3 ratio in the phospholipids was 0.9 in the n-3 cells and 13.1 in the n-6 cells compared with 6.3 in controls cells. Such modifications did not alter action potentials and the main parameters related to contraction, although shortening was slightly accelerated in the n-6 cells. On the other hand, the positive chronotropic effect induced by isoproterenol was more pronounced (P < 0.01) in n-3 cells than in n-6 cells. In addition, isoproterenol caused a decrease in contraction duration and in shortening and relaxation time that was less pronounced in n-6 than in control cells (P < 0.01, P < 0.01 and P < 0.05, respectively). These results suggest that the PUFA balance in the phospholipids may contribute to modulate the cardiac adrenergic receptor system but not the membrane properties related to electromechanical functions.