Chronic ethanol treatment affects synaptosomal membrane-bound enzymes.
A progressive increase in activity of some brain membrane-bound enzymes is shown after 2 and 4 weeks of ethanol administration. After 4 weeks the activities in brain homogenate of (Na+, K+) ATPase, Ca++ ATPase, 5'-nucleotidase, acetylcholinesterase and adenylate cyclase increased 150, 200, 140, 125 and 129 percent, respectively. Arrhenius plots of synaptosomal (Na+, K+) ATPase and acetylcholinesterase from alcohol-treated rats showed a lower transition temperature than control rats after two weeks, and this changed to a higher transition temperature after 4 and 8 weeks. Also, when ethanol was added in vitro to the control membranes, the transition temperature was lowered. However, if the alcohol was added to the membranes from alcohol-treated animals, the transition temperature was lowered to a value similar to that of controls. Fluorescence studies with l-anilinonaphthalene-8-sulfonate (ANS) demonstrate that ethanol induces a decrease in the fluorescence of ANS bound to brain synaptic membranes. This decrease in fluorescence is less than when these membranes are derived from chronically ethanol-treated rats. Also, when the synaptosomal enzymes were exposed to exogenous agents such as detergents, the enzyme obtained from alcohol-treated rats was more stable than that from control rats. These findings indicate a protein conformation change, probably due to the alteration of the physical properties of membrane lipids following chronic ethanol administration. These findings also demonstrate that there is a resistance to the effect of ethanol in membranes of animals habituated to ethanol that may be related to the adaptative modifications that underlie tolerance to and physical dependence on alcohol.
D015720:5'-Nucleotidase; D000110:Acetylcholinesterase / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004798:Enzymes / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology*; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism; D009708:Nucleotidases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013570:Synaptic Membranes / Q000187:drug effects* / Q000201:enzymology; D013574:Synaptosomes / Q000187:drug effects* / Q000201:enzymology; D013696:Temperature
D004798:Enzymes; D008565:Membrane Proteins; D000431:Ethanol; D000110:Acetylcholinesterase; D009708:Nucleotidases; D015720:5'-Nucleotidase; D000262:Adenylyl Cyclases; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase