In vitro influences of alcohols on mouse synaptosomes, and structure-activity relationships

Abstract

Little information is available on the structure-central nervous system membrane toxicity relationship of alcohols. The purpose of the present study was to study in vitro influence of alcohols (n = 20) on the activity of the toxic indicator Na+/K(+)-adenosine triphosphatase (Na+/K(+)-ATPase) and acetylcholinesterase (AchE), and membrane fluidity in mouse brain synaptosomes, in terms of the structure-activity relationship. The potency of inhibition for the enzymes (IC50) and the potency of increasing membrane fluidity (IC12.5) were determined experimentally, and n-octanol/water partition coefficient (P) and the steric constant Taft Es are cited from the literature. Regression analysis revealed that log 1/IC50 for Na+/K(+)-ATPase is a function of log P and Taft Es. The situation was true for AchE activity. The results indicate that the hydrophobicity expressed as log P and the steric effect of the alcohols play an important role in inhibiting both enzyme activities. A linear relationship between log 1/IC12.5 for membrane fluidity and log P is shown, indicating a significant effect of the alcohols on membrane fluidity. Based on these results, it is suggested that the alcohols inhibit the Na+/K(+)-ATPase and AchE activity through a direct action on the enzymes and/or through changing the membrane fluidity.

Synaptic plasma membrane-bound acetylcholinesterase activity is not affected by docosahexaenoic acid-induced decrease in membrane order

“…This finding contrasts with the increased activity of synaptosomal AChE found in rats fed high versus low 18:2/18:3 diets (Foot et al, 1983). Our results also contrast with those of several other studies, where aqueous (Tanii et al, 1995), organic (Edelfors and Ravn-Jonsen, 1992;Engelke et al, 1992) or anesthetic compounds (Ondrias et al, 1983;Sidek et al, 1984;Mazzanti et al, 1986) were shown to alter AChE activity with concomitant changes in DPHdetermined membrane disorder of the SPM. Although it is difficult to account for this discrepancy, it may be considered that these organic molecules were encountered by the acyl chains of the phospholipid bilayer acyl chain as an extrinsic factor, whereas DHA after in vivo administration is intrinsically esterified to the phospholipid glycerol backbone.…”

“…If DHA exerts a similar influence on fluidity in the SPM, it could be expected that DHA would also affect the activity of SPMbound AChE. Alterations of brain synaptic plasma membrane fluidity by ethanol (Tanii et al, 1995), benzene (Engelke et al, 1992), toluene (Edelfors and Ravn-Jonsen, 1992) and several anaesthetics (Ondrias et al, 1983;Sidek et al, 1984;Mazzanti et al, 1986) may influence the activity of SPM-bound enzyme such as AChE. Dietary cholesterol, which inversely relates to membrane fluidity (Hashimoto et al, 1999a,b;Hossain et al, 1999a,b), affects synaptosomal AChE activity (Sanchez-Yague et al, 1991).…”

Effects of Insecticides on the Fluidity of Mitochondrial Membranes of the Diamondback Moth,Plutella xylostella, Resistant and Susceptible to Avermectin

“…The applied concentration of DPH was based on previous reports (Ohyashiki et al 1992; Tanii et al 1995), and the DPH stock solution (2 mM) was prepared in tetrahydrofuran and was diluted 1000-fold by injection into a vigorously stirred solution of PBS (10 mM buffer, pH 7.4, 0.14 mol/L NaCl), and stirred for 1 h before use. Briefly, the diluted mitochondrial membranes were mixed with the fluorescent probe DPH (0.3 mg protein/ml, 2 µM DPH).…”

Effects of vitamin E supplementation on plasma membrane permeabilization and fluidization induced by chlorpromazine in the rat brain

“…CPZ (100 M) was added to DPH-labeled membrane preparations (0.07 mg protein/mL) and incubated at 36°C for 10 min. The 10-min incubation period was based on a pilot experiment in which the maximum effect of CPZ on the membrane anisotropy described below was reached after 10 min of incubation, findings in accord with those for alcohols (Tanii et al, 1995) and other organic solvents (Huang et al, 1993;Tanii et al, 1994). The final concentration of the vehicle (DMSO) in the reaction mixture was 1%.…”

“…1,6-Diphenyl-1,3,5-hexatriene (DPH) is the most frequently employed fluorescent probe which distributes throughout the hydrophobic core of the membrane bilayer (Shinitzky and Barenholz, 1978). The decrease in the fluorescence anisotropy of DPH indicates increased mobility of the probe and thus reflects the fluidization or disordering of the membrane core (Ohyashiki et al, 1992;Huang et al, 1993;Tanii et al, 1994Tanii et al, , 1995.…”