Guillaume D, Grisar T, Delgado-Escueta AV, Minet A, Vergniolle-Burette M, Bureau-Heeren M. Phenytoin dephosphorylates the alpha(-) catalytic subunit of (Na+, K+)-ATPase. A study in mouse, cat and human brain.
Biochem Pharmacol 1989;
38:3933-9. [PMID:
2557036 DOI:
10.1016/0006-2952(89)90670-9]
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Abstract
Phenytoin, a potent antiepileptic drug, has been thought to stimulate Na+, K+ transport across cell membranes, but its influence on (Na+, K+)-ATPase activity remains highly controversial. We have investigated the effects of the drug on the phosphorylation level of (Na+, K+)-ATPase partially purified from mouse, cat and human brain. (Na+, K+)-ATPase catalytic subunits [alpha(+) and alpha(-)] were resolved by sodium dodecylsulfate polyacrylamide gel electrophoresis. Previous experiments had shown that phenytoin dephosphorylates the (Na+, K+)-ATPase catalytic subunit by +/- 50% in C57/BL mice. In the present study, we showed that phenytoin (10(-4) M) decreases the phosphorylation level of (Na+, K+)-ATPase catalytic subunit by the same value in cat and human cortex. Moreover, that effect is predominant on the alpha(-) subunit, thought to be the predominant enzymatic form in non-neuronal or glial cells. The results are thus favoring the hypothesis that phenytoin stimulates the brain (Na+, K+)-ATPase. They further suggest that phenytoin mainly activates the glial enzymatic form, providing central nervous system with an enhanced ability to regulate extracellular K+.
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