genic importance of arterionecrosis in stroke in SHRSP; cerebral bleeding is caused by the rupture of microaneurysms induced at the weakened arterionecrotic wall, and cerebral infarction is caused by thrombosis at the site of arterionecrosis (Yamori

Stroke-prone SHR (SHRSP) are regarded as being proper animal models for stroke in man (Yamori et al: Clin Exp Pharmacol Physiol (Suppl) 3: 199, 1976, Handa et al: In "Spontaneous Hypertension" 294, DHEW Publication No. (NIH) 77-1179, 1977). Studies on the pathogenesis of stroke confirmed the pathogenic importance of arterionecrosis in stroke in SHRSP; cerebral bleeding is caused by the rupture of microaneurysms induced at the weakened arterionecrotic wall, and cerebral infarction is caused by thrombosis at the site of arterionecrosis (Yamori et al: Stroke 7: 46, 1976, Yamori et al: Progress in Brain Research 47, "Hypertension and Brain Mechanisms", 219, Elsevier, Amsterdam, 1977). Initiation mechanism of arterionecrosis is the increased permeability of the arterial wall that is especially due to severe hypertension (Yamori et al: Jap Circulat J 39: 611, 1975). Whether such an increase in vascular permeability is related to biomembrane characteristics of vascular walls remains unsolved. Therefore, as a simplified model of biomembrane in SHR, osmotic fragility of erythrocyte membrane was examined by exposing erythrocytes to osmotic stress by the coil planet centrifugation (Ito et al: Nature 212: 985, 1966, Ito et al: Anal Chem 41: 1579, 1968).