title: Specific inactivation of alpha (+) molecular form of (Na+ + K+)-ATPase by pyrithiamin.
abstract: We have recently reported that pyrithiamin inhibits the activity of (Na+ + K+)-ATPase derived from neuronal but not non-neuronal tissue. In view of the recent demonstration that there are two molecular forms of (Na+ + K+)-ATPase in brain, the present study has examined which form of the enzyme is selectively inhibited by pyrithiamin. Experiments with sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the treatment with pyrithiamin decreased the phosphorylation by [gamma-32P]ATP of alpha (+) in a dose-dependent manner while it had little effect on that of alpha. Furthermore, the treatment with pyrithiamin changed the sensitivity of the enzyme to ouabain and N-ethylmaleimide. The specificity of the action of pyrithiamin for alpha (+) was further examined in the developing rat brain (Na+ + K+)-ATPases and peripheral (Na+ + K+)-ATPases from various animals. The molecular form of rat brain (Na+ + K+)-ATPase was primarily alpha on the 14th day of gestation, while it was mainly alpha (+) on the 18th day of gestation and postnatal age. The enzyme from 14-day fetal rat brain was resistant to pyrithiamin inhibition more than other brain enzymes. In cardiac and renal (Na+ + K+)-ATPases from various animals, only the alpha molecular form was found except for dog cardiac preparation which contained alpha (+) and alpha. Pyrithiamin inhibited dog cardiac enzyme activity, while it exerted only minimal inhibition on other peripheral enzymes. It is concluded that pyrithiamin selectively inactivates the alpha (+) molecular form of (Na+ + K+)-ATPase.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D004285:Dogs; D006168:Guinea Pigs; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009206:Myocardium / Q000201:enzymology; D009474:Neurons / Q000201:enzymology*; D009928:Organ Specificity; D011726:Pyridinium Compounds / Q000494:pharmacology*; D011745:Pyrithiamine / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013045:Species Specificity
chemical_list: D046911:Macromolecular Substances; D011726:Pyridinium Compounds; D011745:Pyrithiamine; D000254:Sodium-Potassium-Exchanging ATPase