MEMBRANE MICROVISCOSITY AND PLASMA TRIACYLGLYCEROLS IN THE RAT

1. Multiple cell membrane alterations have been described in humans an d animals with various genetic forms of hypertension and/or dyslipidae mia, The aim of our study was to characterize membrane microviscosity, using two different fluorescent probes exploring either the outer mem brane leaflet [trimethylamino-diphenylhexatriene (TMA-DPH)] or the lip id membrane core [diphenylhexatriene (DPH)], in platelets and erythroc ytes of genetically hypertensive rats of the Prague hereditary hypertr iglyceridaemic (HTG) strain, The relationships of membrane microviscos ity to hypertension, hypertriglyceridaemia and cell calcium handling w ere also investigated. 2. Membrane microviscosity was similar in HTG a nd normotensive control Wistar rats when measured in platelets or eryt hrocyte ghosts incubated in Na+-containing medium. On the contrary, TM A-DPH fluorescence anisotropy was significantly reduced in HTG platele ts incubated in Na+-free medium because external Naf removal elicited a larger rise of TMA-DPH anisotropy in Wistar platelets. 3. Plasma tri acylglycerols were associated positively with platelet TMA-DPH anisotr opy and negatively with DPH anisotropy in both strains, The slopes of these relationships were reduced in HTG compared with Wistar rats, Pla telet TMA-DPH anisotropy correlated positively and DPH anisotropy nega tively with the cytosolic calcium concentration in unstimulated platel ets, the slopes being almost identical in both strains. 4. Pulse press ure correlated negatively with TMA-DPH anisotropy and positively with DPH anisotropy found in erythrocyte ghosts. 5. The present results sug gest that plasma triacylglycerols and cytosolic calcium are capable of modulating the membrane microviscosity in this new animal model of ge netic hypertension associated with hypertriglyceridaemia.