Phenobarbital modulates the (Na+, K+)-stimulated ATPase and Ca2+-stimulated ATPase activities by increasing the bilayer fluidity of dog brain synaptosomal plasma membranes.
The binding of [14C]phenobarbital into synaptosomal plasma membranes of dog brain follows a sigmoid path. The "best fit" curve of this binding is the one described by the Hill equation (r2 less than 0.93 and Hill coefficient, n = 1.32). (Na+, K+)-stimulated ATPase and Ca2+-stimulated ATPase activities are modulated by phenobarbital. Arrhenius plots of (Na+, K+, Mg2+)-dependent ATPase revealed that phenobarbital (2 mM) lowered the transition temperature and altered the Arrhenius activation energies of this enzyme. The allosteric inhibition by F- of the (Na+, K+)-stimulated ATPase was studied in control and phenobarbital-treated membranes. The lowering of the transition temperature and changes in Arrhenius activation energy about the transition temperature in combination with changes observed in the allosteric properties of the (Na+, K+)-stimulated ATPase by F-, produced by phenobarbital, would be expected if it is assumed that phenobarbital "fluidizes" synaptosomal plasma membranes.
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000201:enzymology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004285:Dogs; D008560:Membrane Fluidity / Q000187:drug effects*; D010634:Phenobarbital / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013268:Stimulation, Chemical; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology; D013696:Temperature
D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D010634:Phenobarbital