All issues > Volume 34(7); 1991

Original Article

J Korean Pediatr Soc. 1991;34(7):959-970. Published online July 31, 1991.

Experimental study on the effect of phenobarbital on Na+, K+-activated adenosine triphosphatase in microsome fractions of mouse brain.

Seo Kyu Kim¹, Sa Jun Chung¹, Chang Il Ahn¹

¹Department of Pediatrics, College of Medicine, Kyung Hee University, Seoul, Korea

Received: February 28, 1991;  Accepted: April 18, 1991.

Abstract

Na+, K+-activated adenosine triphosphatase (Na+, K+-ATPase) is known to play a role as a trigger in neurotransmitter release and may also affect the transport of calcium ion (Ca++). By doing so, Na+, K+-ATPase, as an anticonvulsant, can modify the excitability level of cells in epilepsy. In order to elucidate the possible mechanisms of neuropharmacological interaction between Na+, K+.ATPase and phenobarbital, serial experimental studies were carried out. Na+, K+-ATPase activities were measured in microsome fractions of mouse brain. The measure- ment of Na+, K+-ATPase was performed using Fiske-Subbarow’s method-the colorimetric determina- tion of phosphorus, and determination of the protein was made by the method of Lowry and his colleagues. Some of the major findings were as follows:- 1) The activity of Na+, K+-ATPase was inhibited by 14.6, 17.7, and 19.8% on average by adding each phenobarbital 0.01, 0.10, and 1.00 mM. No statistical difference was observed by dosage of the varying concentrations of phenobarbital. 2) The activity of Na+, K+-ATPase was inhibited by 87.6% by adding ouabain and further addition of each phenobarbital 0.01, 0.10, and 1.00 mM inhibitied Na+, K+-ATPase by 98.6, 99.9, and 99.9%, i.e. further inhibition of 11.0, 12.3, and 12.3%. No statistical difference was observed by dosage of the varying concentrations of phenobarbital 3) The activity of Na+, K+-ATPase was stimulated by 74.7% by adding GABA and further addition of each phenobarbital 0.01, 0.10, and 1.00 mM inhibited Na+, K+-ATPase activity by 17.7,12.3, and 12.3%. No statistical difference was observed by dosage of the varying concentrations of phenobar- bital. 4) The mean percentage of inhibition of the activtiy of Na+, K+-ATPase 19.8% by adding phenobarbital 1.00 mM by further adding of ouabin, Na+, K+-ATPase activity was inhibited by 90. 9%, and 88.4% of enzyme activity was increased by adding GABA. By further adding of phenobar- bital 1.00 mM, Na+, K+-ATPase activity was inhibited by 20.7%. Therefore, these findings strongly suggested that phenobarbital had inhibitiory effect on Na+, K+-ATPase activity. 5) By increasing the ratio of Na+, K+, the inhibitory effect of phenobarbital on Na+, K+-ATPase activity was not changed at the varying concenttations of 20, 40, 80 mM Na in 17 mM K. 6) By increasing the ratio of Na+, K+, the inhibitiory effect of phenobarbital on Na4、K+-ATPase activity was not changed at the varying concentration of 2, 10, and 17 mM K in 80 mM NaCl. With the above mentioned results, the following hypothesis can be formulated. Phenobarbital has a direct inhibitiory effect of Na+, K+-ATPase by which it may increase the influx of Ca ion (Ca++) by influencing Na+/Ca++ exchange system. Phenobarbital may also act as a trigger for the release of putative neurotransmitter, and which enhance GABA response by enhancing GABA binding to GABA receptor or modifying chloride ion channel properties.

Keywords :Phenobarital Na+;K+ -ATPase activry;Mouse brain