Dantrolene Inhibits Human Erythrocyte Glutathione Reductase

Dantrolene, a drug used to treat malignant hyperthermia, inhibits abnormal Ca2+ release from the sarcoplasmic reticulum. Glutathione reductase (Glutathione: NADP+ oxidoreductase, EC 1.8.1.7), a member of the pyridine-nucleotide disulfide oxidoreductase family of flavoenzymes, catalyzes the reduction of glutathione disulfide (GSSG) to reduced form (GSH) in the presence of nicotinamide adenine dinucleotide phosphate (NADPH). In the present study, the in vitro effects of dantrolene on human erythrocyte glutathione reductase were investigated. For this purpose, initially, human erythrocyte glutathione reductase was purified 2555.56 fold in a yield of 29.74% using both 2',5'-ADP Sepharose-4B affinity gel chromatography and Sephadex G-200 gel filtration chromatography. The purity of the enzyme was controlled by sodium dodecyle sulfate (SDS)-polyacrylamide gel electrophoresis (SDS-PAGE) which showed a single band. A constant temperature (+4 degrees C) was maintained during the purification process. Enzyme activity was determined with the Beutler method at 340 nm by means of a spectrophotometer. Dantrolene showed remarkable in vitro inhibitory effects on the enzyme. K-i constant and 50% inhibitory concentration (IC50) value for dantrolene were determined by Lineweaver-Burk graphs and plotting activity % vs. [I], respectively. K-i constant for dantrolene was found to be 0.1116 +/- 0.04 mM; IC50, value was 0.0523 mM. Dantrolene displayed non-competitive inhibition.