D-MYO-INOSITOL DERIVATIVES ALTER LIPOSOMAL MEMBRANE FLUIDITY

We investigated the effect on membrane fluidity induced by D-myo-inosi tol derivatives (IP3, IP4, IP5, IP6). Fluidity was determined as the a nisotropy of fluorescence polarisation fi om liposome model membranes labelled with DPH (1,6-diphenyl-1,3,5 hexatriene). IP3 (10(-10) to 10( -5) M) increased the membrane fluidity with a maximum effect at 10(-5) M. For IP4, IP5 and IP6, at concentrations less than 10(-6) M these d erivatives increased the membrane viscosity (i.e. reduced fluidity). T his effect was enhanced when the derivatives were incorporated in the vesicles, rather than added to the vesicle suspension. In this case IP 5 and IP6 increased viscosity over the reference values. We conclude t hat inositol derivatives directly modified membrane fluidity which cou ld play a role in their effects in biological systems, beside the one mediated by binding to specific receptors.