HIGH POTASSIUM DIETS REDUCE VASCULAR AND PLASMA-LIPID PEROXIDES IN STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS

We examined the effect of high potassium (K) diet on oxidative stress to endothelium in hypertensive rats. Five-week-old stroke-prone sponta neously hypertensive rats(SHRsp) were fed a 5% high NaCl diet containi ng either 0.5% normal K (n=28) or 2.1% high K (n=19) for 6 weeks, and lipid peroxides in the aortic intima and plasma were measured. Lipid p eroxides were extracted into an organic solvent to avoid the interfere nce of carbohydrates or glycoproteins, and malondialdehyde (MDA) produ ced from lipid peroxides by acid-heating was measured by its reaction to thiobarbituric acid. The antioxidant butylated hydroxytoluene preve nted spurious lipid peroxide formation during the whole procedure, and optimum Fe3+ allowed a maximum MDA production from lipid peroxides. T he high K SHRsp showed lower lipid peroxide levels than the normal K S HRsp both in the intima (5.6 +/- 0.3 vs. 7.2 +/- 0.4 nmol MDA/mg fatty acids, p<0.003) and plasma (0.91 +/- 0.08 vs. 1.46 +/- 0.10 nmol MDA/ ml, p<0.001). Mean arterial pressure was slightly lower by 13 mmHg in the high It SHRsp, but these differences were still obvious even when we compared groups of rats with precisely matching blood pressures. Th ese results indicate that high K diets reduce oxidative stress on the endothelium of high NaCl-fed SHRsp independently of blood pressure cha nges. This effect may be involved in the mechanism by which high K die ts protect endothelium and reduce stroke incidence in hypertensive ani mals. Thus, we improved the method of lipid peroxide measurement and p ropose the protective effects of high K diet against oxidative stress to endothelium in hypertensive animals.