EFFECTS OF DIETARY FISH-OIL ON CARDIOVASCULAR RESPONSIVENESS TO ADRENERGIC AGONISTS IN SPONTANEOUSLY HYPERTENSIVE RAT

To test the hypothesis that dietary fish oil supplementation decreases SyStolic blood pressure in hypertensive rats by modifying cardiovascu lar responsiveness to adrenergic agonists, spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) received either a com or fish o il diet, 5% (g/kg) for 10 weeks. Mean aortic pressure was lower in fis h oil treated (161 +/- 7 mm Hg (1 mmHg = 133.3 Pa)) than com oil treat ed (191 +/- 6 mmHg) SHR. Although dietary fish oil supplementation dec reased responsiveness to norepinephrine in isolated thoracic aorta fro m SHR, there was no change in cardiovascular responsiveness to the bet a1 agonist dobutamine or the alpha1 agonist phenylephrine when these a drenergic agonists were administered in vivo. However, dietary fish oi l did decrease the spontaneous basal tone in aorta from both SHR and W KY. This study provides further evidence that dietary fish oil lowers blood pressure in an animal model genetically predisposed to hypertens ion. However, the mechanism for this decrease in mean aortic pressure in vivo does not appear to be related to modification of cardiovascula r responsiveness to alpha1- or beta1-adrenergic agonists and may be re lated to a decrease in basal vasomotor tone.