High potassium diets reduce endothelial permeability in stroke-prone spontaneously hypertensive rats

1. High potassium (K) diets are known to prevent hypertensive arterial lesions and reduce stroke incidence without affecting blood pressure. 2. To elucidate the mechanism of this beneficial effect, we studied the effect of K supplementation on the extravasation of plasma albumin in high NaCl-fed stroke-prone spontaneously hypertensive rats (SHRSP). Increased permeability of the endothelium to macromolecules is assumed to be an early manifestation of vascular injury. 3. The disappearance of intravenously injected [125I]-albumin was examined in SHRSP rats fed high NaCl diets containing either 0.5% normal K or 2.1% high K for 5 weeks. 4. The bodyweight, blood pressure, plasma volume and urinary protein excretion were not significantly different between the two SHRSP groups. 5. The high K SHRSP showed a slower plasma albumin disappearance rate than the normal K SHRSP (10.3 vs 14.7%/h, P < 0.004). The albumin radioactivity remaining in the aortic wall and in the brain after removing blood after perfusion was lower in the high K SHRSP than in the normal K SHRSP (aorta, -20%, P < 0.02; brain, -26%, P < 0.04). 6. These results suggest that the high K diet reduced the endothelial permeability to albumin in high NaCl-fed SHRSP rats. High K diets may have a protective effect against endothelial dysfunction and thereby contribute to the reduction of vascular lesion formation and stroke incidence.