Evidence of altered permeability of the erythrocyte membrane for sodium and potassium ions in spontaneously hypertensive rats.

1. Erythrocyte membrane permeability to sodium and potsssium ions was studied in 8-10 weeks spontaneously hypertensive rats (SHR, Kyoto/Wistar strain), normotensive Wistar and Sprague-Dawley rats. 2. The rate of 22Na efflux from the erythrocytes and the rate constant of Na/Na exchange were considerably greater in SHR than in normotensive Wistar and Sprague-Dawley rats. This difference remained the same in rats adrenalectomized 7 days before the experiment. The maximum difference in the constants was found when the sodium-potassium pump was blocked by ouabain. 3. The accumulation of 42K in the erythrocytes of SHR (the sodium-potassium pump being blocked) took place at a considerably slower rate, and the K+ wash-out into a potassium-free medium was faster than that in the normotensive Wistar and Sprague-Dawley rats. 4. These results indicate a higher permeability of the erythrocyte membrane of SHR for Na+ and K+, compared with normotensive Wistar and Sprague-dawley strains. It is suggested that this may reflect a more widespread cell-membrane defect, which could serve as a general cause for activating the mechanisms maintaining high blood pressure.