Figure 15.

Representative effects of Gd⁺³ and CPZ on membrane anisotropy. Vesicles were isolated as described in materials and methods. Arrows indicate experimental changes. (A) Addition of Gd⁺³ caused a slow time-dependent decrease of anisotropy. This decrease was not dose dependent in that similar effects were observed with 50 and 100 μM Gd⁺³. As these experiments used DPH-HPC, which is an outer leaflet specific probe, these changes reflect effects of Gd⁺³ on the outer membrane leaflet. Data representative of five experiments. (B) Addition of CPZ caused a decrease of membrane anisotropy with a much faster time course than that observed with Gd⁺³. Data representative of four experiments. (C) Preincubation of vesicles at 4°C prevented the actions of Gd⁺³ on membrane anisotropy. These effects are consistent with those observed in Fig. 14 demonstrating the elimination of the effects of Gd⁺³ on C_m and the altered blocking kinetics of g _m, in oocytes precooled to 4°C. These findings are taken as further support of the membrane actions of Gd⁺³. Data representative of three experiments.