EFFECTS OF ETHANOL ON STRUCTURAL PARAMETERS OF RAT-BRAIN MEMBRANES - RELATIONSHIP TO GENETIC-DIFFERENCES IN ETHANOL SENSITIVITY

Fluorescent probes located in different membrane regions were used to evaluate effects of ethanol (50 and 100 mM) on structural parameters ( protein distribution, fluidity of total and annular lipid, and thickne ss of the bilayer) of synaptic plasma membranes (SPMs) from brain cort ex of High-Alcohol Sensitivity (HAS) and Low-Alcohol Sensitivity (LAS) rats. An experimental procedure based on radiationless energy transfe r from tryptophan of membrane proteins to pyrene, 1,3-bis-(1-pyrene)pr opane(pyr-C-3-pyr), or 1,6-diphenyl-1,3,5-hexatriene (DPH), as well as pyr-C-3-pyr monomer-eximer formation end DPH polarization, and energy transfer from pyrene monomers to 1-anilinonaphthalene-8-sulfonic acid (ANSA) was utilized. The efficiency of energy transfer from tryptopha n to pyrene was sensitive to protein clustering induced in SPMs by con canavalin A. Efficiency of energy transfer from pyrene monomers to ANS A was different for vesicles of dimyristoyl phosphatidyl choline, dipa lmitoyl phosphatidyl choline, and distearoyl phosphatidyl choline, con sistent with differences in the thickness of these lipid bilayers. Wit hout ethanol, there were no significant differences between the struct ural parameters of SPMs from HAS and from LAS rats. Addition of ethano l (50 mM) changed protein distribution (increased clustering) only in membranes from HAS rats and had no effect on the structure of membrane s from LAS rats. A larger concentration of ethanol (100 mM) changed th e fluidity of annular and total lipid in both lines of rats, but chang ed protein distribution end decreased thickness of the membranes from HAS rats with no effect on these parameters in SPMs from LAS animals. Ethanol (50 and 100 mM) decreased the binding affinity of ANSA for mem branes from HAS, but not LAS rats. Genetic differences in ethanol sens itivity of HAS and LAS rats may be related to effects of ethanol on pr otein mobility, protein-protein interactions, or membrane thickness, b ut do not appear to be due to effects of ethanol on the fluidity of me mbrane lipids.