In vitro effects of some drugs on human erythrocyte glutathione reductase

Abstract

The effects of ketotifen, meloxicam, phenyramidol–HCl and gadopentetic acid on the enzyme activity of GR were studied using human erythrocyte glutathione reductase (GR) enzymes in vitro. The enzyme was purified 209-fold from human erythrocytes in a yield of 19% with 0.31 U/mg. The purification procedure involved the preparation of haemolysate, ammonium sulphate precipitation, 2′′,5′-ADP Sepharose 4B affinity chromatography and Sephadex G-200 gel filtration chromatography. Purified enzyme was used in the in vitro studies. In the in vitro studies, IC₅₀ values and K_i constants were 0.012 mM and 0.0008 ± 0.00021 mM for ketotifen; 0.029 mM and 0.0061 ± 0.00127 mM for meloxicam; 0.99 mM and 0.4340 ± 0.0890 mM for phenyramidol–HCl; 138 mM and 28.84 ± 4.69 mM for gadopentetic acid, respectively, showing the inhibition effects on the purified enzyme. Phenyramidol–HCl showed competitive inhibition, whereas the others showed non-competitive inhibition.

Keywords::

• Glutathione reductase
• drugs
• inhibition