EFFECTS OF LINDANE ON MICROVISCOSITY OF BRAIN MEMBRANES

We studied the influence of lindane on the microviscosity of synaptosomal plasma membrane vesicles (SPMV) isolated from bovine cerebral cortex and liposomes (SPMVPC) of phosphatidylcholine (PC) fraction extracted from SPMV. Changes in the microviscosity were measured by the intramolecular excimerization of 1,3-di(1-pyrenyl) propane(Py-3-Py). The excimer to monomer fluorescence intensity ratio of Py-3-Py in liquid paraffin was a simple linear function of absolute temperature per dynamic viscosity (T/eta). Based on this calibration curve, the microviscosity values of the direct probe environment in SPMV ranged from 575.99 +/- 185.16 cP at 4 degrees C to 29.06 +/- 1.25 cP at 45 degrees C. And the value changed from 233.59 +/- 37.12 cP at 4 degrees C to 20.93 +/- 0.79 cP at 46 degrees C in SPMVPC. At 37 degrees C, the values in SPMV and SPMVPC were 38.17 +/- 1.90 and 26.41 +/- 1.03 cP, respectively. Although smaller effects were observed in SPMVPC, lindane significantly decreased the microviscosity of both SPMV and SPMVPC in a concentration-dependent manner. This indicates that the direct environment of Py-3-Py in both membranes is significantly fluidized by lindane. Thus, the present study shows that an interaction between the drug and membrane lipids is of importance in the molecular mechanism of action and, possibly, toxicity of lindane.