Advertisement
Research Article Free access | 10.1172/JCI106909
Department of Neurology, Mount Sinai School of Medicine of the City University of New York, New York 10029
Department of Physiology, Mount Sinai School of Medicine of the City University of New York, New York 10029
Institute for Medical Research and Studies, New York 10010
Find articles by Siegel, G. in: JCI | PubMed | Google Scholar
Department of Neurology, Mount Sinai School of Medicine of the City University of New York, New York 10029
Department of Physiology, Mount Sinai School of Medicine of the City University of New York, New York 10029
Institute for Medical Research and Studies, New York 10010
Find articles by Goodwin, B. in: JCI | PubMed | Google Scholar
Published May 1, 1972 - More info
Effects of diphenylhydantoins on (Na+ + K+)-ATPase activity in rat and cat brain microsomes were studied. 5,5-diphenylhydantoin (DPH) in concentrations of 5-20 μg ml-1 produces an apparent stimulation of the rat brain (Na+ + K+)-activated ATPase of 55-65% in media containing 50 mM Na+, 0.15 mM K+, 3 mM Mg++, and 3 mM ATP. No effects are found on the Mg-ATPase. At constant K+ levels of 0.05 mmole/liter and 0.15 mmole/liter, increasing the Na+ concentration activates the enzyme similarly with and without DPH. However, Na+ concentrations greater than 5 mmoles/liter and 10 mmoles/liter, respectively, which are inhibitory in these low K+ media, produce less inhibition in the presence of DPH. In media containing 10 mM Na+, the K+ activation, on the other hand, is potentiated by DPH. In preparations from cat brain qualitatively similar results are obtained. No effect of DPH is seen on the inhibition produced by high K+ in low Na+ media. DPH produces an approximately constant apparent stimulation of 45% in the (Na+ + K+) increments when these ions are varied simultaneously at a fixed ratio of 150 Na+:1 K+ with cat brain extracts. 5-(p-hydroxyphenyl)-5-phenylhydantoin (HPPH) has the same potency as DPH in reducing the Na+ inhibition at high Na:K ratios. The hydantoins appear to act by decreasing the Na+ inhibition that occurs at high Na:K ratios.