1. Diphenylhexatriene was used as a fluorescence probe to detect structural differences between membranes from genetically hypertensive rats and those from their normotensive controls. Both isolated membranes (erythrocyte ghosts) and whole cells (platelets) were studied.
2. In the Okamoto-Aoki strain, the fluorescence polarization of diphenylhexatriene and consequently the ‘equivalent microviscosities' were altered in all membranes, even in those of young normotensive SHR. These abnormalities varied with age (in whole cells) and were not detected in females.
3. These alterations were not restricted to the SHR strain and were also observed in the Sabra hypertensive strain (SBH). The ‘equivalent microviscosity’ of hypertensive Sabra erythrocyte ghosts was higher than that of the original Sabra rats. Salt loading of the Sabra rats promoted an increase in the ‘equivalent microviscosity’ of their erythrocyte membranes, which nearly reached the Sabra hypertensive level.
4. These results support the hypothesis of a genetic change in hypertensive rats leading, directly or indirectly, to diffuse alterations of cell membrane structure, which seem to be similar to those caused by high salt intake.