From these results, it is confirmed that generalized and focal signs, such as paraparesis or hemiparesis which are observed at the symptomatological grades 2, 3 and 4 SHRSP do scarcely result from the spinal cord lesions, and therefore, neurological signs and symptoms of SHRSP are manifestations due to cerebral lesions in most cases. In SHRSP, the incidence of cerebral lesions is much higher than that of spinal lesions, among all vascular lesions in the central nervous system as in humans

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From these results, it might be speculated that NaCl directly affect vascular permeability, indifferent to hypertension, suggesting the possible involvement of the nervous system and vascular wall alteration (for example, water logging). However, relationship between blood pressure and serum cholesterol level, and also relationship between NaCl and the nervous system should be further investigated in such models as normotensive atherogenic rats (NAR)

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As we previously reported and reconfirmed, SHRSP fed on the normal diet developed stroke, in average, at the age of 9 months in males. However, in the present study, SHRSP fed on the high protein (soybean protein in this study) diet maintained the normal range in both rCBF and chemical cerebrovascular reactivity in spite of the development of severe hypertension at the age of 8 month. These experimental results substantiated prophylactic effect of high protein diet on stroke from the view point of mechanism of stroke mentioned above in the introduction

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SHRSP fed on the high protein diet showed significantly higher vascular reactivity than those fed on the high fat-cholesterol diet as determined by response in mean pressure, while response in pulse pressure showed the inverse relationship, indicating improvement of vascular elasticity in SHRSP fed on the high protein diet. These experimental results suggest that high protein diet may increase the vascular robustness in SHRSP

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Methionine and taurine attenuated the development of severe hypertension in SHRSP. However cysteine had not such an effect. Methionine also decreased the incidence of stroke in SHRSP (43%) in comparison with the incidences in cysteine-treated and control SHRSP (88 and 89%, respectively). Methionine or taurine may reduce the blood pressure by modulating central blood pressure regulation

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High protein diets containing sulfoamino acids attenuate the development of severe hypertension partly by the central effect on the blood pressure. High soy bean protein diets show no effect on blood pressure, but maintain the elasticity of the arterial wall even after SHRSP become old. Moreover, high protein diets counteract the adverse effect of excess salt intake by increasing urinary sodium excretion in SHRSP

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We tried to obtain hypotensive substances in hot water or cold water extracts from seventy items of fifty five plants. Administered intravenously, fractions from mandarine orange leaves, lily bulbs, bamboo grass, spirulina, leek, bean sprout, chlorella, fomitopsis pinicola, mandarine orange peels, young barley leaves, persimmon leaves, and tomato plant leaves showed marked falls in blood pressure.

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We conclude that the inhibition of high blood pressure with diltiazem suppressed the development of vasuular damages

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WITH DISCUSSION Although platelet function, determined by collagen or ADP-mediated aggregation, was decreased in SHRSP and SHRSR, the vascular collagens from SHRSP and SHRSR induced more extensive aggregation of platelets than that from WK. Changes in platelet volume distribution might reflect the functional changes or might be used as the indicator of not yet defined platelet alteration. Moreover, the impairment of fibrinolytic system (decreased plasminogen activator and increased plasmin inhibitor) was noted in SHRSP and SHRSR and this might be the cause of high incidence of thrombosis in SHRSP with hypertensive vascular damages

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In erythrocyte membrane of SHRSP, Ca influx and release rates were accelerated from hypertension developing stage before Ca-ATPase activities were lowered. These changes were preceded by the onset of hypertension. In cytoplasmic membrane the stractural changes would play more important role than regulation mechanism of Ca influx and Ca release through Ca-ATPase. This present results do not conflict with the Ca effect on tonus of isolated rat aortic strips

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The erythrocytes from stroke-prone SHR (SHRSP) were more fragile than those from stroke-resistant SHR (SHRSR) or Wistar-Kyoto (WK) rats at the age of 2 months. After the chronic administration of saline (1% NaCl in drinking water), blood pressure in both SHRSR and WK was elevated, but the membrane fragility was not changed. Therefore, the membrane characteristics in SHRSP may not be related to their hypertension, but possibly to their stroke-proneness

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Present studies have indicated that there may be a common metabolic abnormality in the pathogenesis of severe hypertension causing stroke and of reactive hypercholesterolemia causing atherosclerosis. In genetically hypertensive rats also predisposed to hypercholesterolemia, a decrease in endogenous taurine level in the liver may be involved in the pathogenesis of both severe hypertension and reactive hypercholesterolemia, because exogenous taurine administration attenuates both severe hypertension and reactive hypercholesterolemia.

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