Vascular relaxation to omega-3 fatty acids: Comparison to sodium nitroprusside, nitroglycerin, papaverine, and D600

The vasorelaxant activity of the omega-3 fatty acids-docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids-in comparison with other known vasodilators-sodium nitroprusside, nitroglycerin, papaverine, and D600-were studied in the isolated rat aorta. The relaxant responses of these vasodilators and fatty acids at concentratios of 1-100 μM were assessed in aortic rings contracted with norepinephrine (NE 10^-6 M) or with KCl (30 mM). Cyclic nucleotide enhancers (sodium nitroprusside, nitroglycerin, papaverine) were more effective in producing relaxation, regardless of the contractile mechanism, i.e., alpha-adrenoceptor stimulation or depolarization. In contrast, the omega-3 fatty acids produced augmented relaxation in NE-contracted vessels. Relaxations produced by DHA (15±2% to 45±10%) were similar to D600 (16±2% to 60±7%) in NE-contracted rings, but not in KCl contracted rings. The responses to D600 and DHA in KCl-contracted vessels were 79±2% to 104±3% and 5±1% to 21±3%, respectively. In another set of experiments, the effects of omega-3 fatty acids in the presence of albumin were examined; no significant differences in the induced relaxant responses were noted. These results suggest that the mechanisms of vascular relaxation, such as cyclic nucleotide elevation and calcium antagonism of potential-operated channels, are different from those induced by the omega-3 fatty acids.