Dietary N-6 and N-3 fatty acids and salt-induced hypertension in the borderline hypertensive rat.

This study examined the effects of salt-loading on blood pressure (BP) development in the borderline hypertensive rat (BHR) and its modification by dietary n-3 and n-6 fatty acids. In experiment 1, 4 groups (n = 10/group) of male BHR receiving 1% NaCl as a replacement for tap water were placed on chow enriched with either olive oil (OL), sunflower oil (SUN), evening primrose oil (EPO) or fish oil for 6 weeks. BP, heart rate, body weight, water, Na+ and K+ intake and urinary output were measured weekly. SUN and fish oil reduced the pressor response to salt seen vs the OL group by 50%, and EPO abolished the pressor response, reducing BP below control levels. The BP response was unrelated to either food intake or water and electrolyte intake and excretion. In experiment 2, male BHR received water +/- 18:3n-6 (0.04 mg/hr in OL via ip pump) or 1% NaCl +/- 18:3n-6 (n = 12/group) for 12 weeks, followed by 2 weeks recovery on tap water. Salt increased BP, and 18:3n-6 decreased this response, but had no effect on animals receiving tap water. In experiment 3, effects of 3 doses of 18:3n-6 (0.04, 0.08, and 0.12 mg/hr) on the pressor response to 1% NaCl were examined. All doses reduced the BP response to salt vs controls with no dose-response. These data suggest that the BHR is genetically salt-sensitive, and that dietary n-3 and n-6 fatty acids can attenuate the cardiovascular response to salt in this model.