Key Points
- To investigate the effect of diphenylhydantoin on sodium-potassium-ATPase enzyme activity in isolated rat cerebral cortical synaptosomes.
- Isolated synaptosomes from rat cerebral cortex using Ficoll density gradients.
- Measured sodium-potassium-ATPase specific activity and inorganic phosphate release under varying concentrations and ratios of sodium, potassium, magnesium, and ATP in the presence and absence of diphenylhydantoin.
- Diphenylhydantoin produced an average 92% stimulation of inorganic phosphate release above control at 50 mM sodium and 0.2 mM potassium.
- Enzyme activity stimulation depended on the sodium-to-potassium ratio, with significant stimulation observed at high ratios (25–50:1), minimal effect at intermediate ratios (5–10:1), and inhibition at ratios below 5:1.
- Diphenylhydantoin produced no apparent change in enzyme affinity for ATP across all examined ionic conditions.
Structured PICO
PPopulationRat cerebral cortical synaptosomes isolated in Ficoll gradients
IInterventionDiphenylhydantoin (DPH)
CComparatorControl (no DPH)
OOutcomeNa-K-ATPase enzyme activity (measured by P(i) release)surrogate
Diphenylhydantoin stimulates Na-K-ATPase activity under high Na:K ratios, suggesting a potential mechanism for its seizure-controlling effects.