1. The membrane viscosity of erythrocytes and synaptosomal membranes from 3-month-old stroke-prone spontaneously hypertensive rats (SHRSP) was less than that of normotensive Wistar-Kyoto (WKY) rats.
2. The percentage noradrenaline release from synaptosomes in response to a low potassium ion concentration and the incorporation of noradrenaline into synaptosomes were significantly increased in 3-month-old SHRSP compared with WKY rats.
3. Cultured smooth muscle cells obtained from the aorta of SHRSP showed a greater Na+ influx and K+ efflux when Na+, K+-dependent ATPase was inhibited by ouabain than did smooth muscle cells from the aorta of WKY rats.
4. These results suggest that diverse membrane abnormalities are present in SHRSP, including changes in synaptosomal function and the ionic transport and permeability of smooth muscle cells. These changes may be part of the mechanisms of hypertension, whereas the changes in the erythrocytes may serve as genetic markers of hypertension.