In Vitro Effects of Some Antibiotics on Glutathione Reductase Obtained from Chicken Liver

Authors: HÜLYA DEMİR, MUSTAFA ERAT, HALİS ŞAKİROĞLU

Abstract: Glutathione reductase (GR) is important in maintaining high levels of reduced glutathione in cells. The enzyme is inhibited by some drugs used in antimicrobial chemotherapy. The effects of some antibiotics on GR activity were investigated in this study. At first, the enzyme, having a specific activity of 88.28 EU/mg proteins, was purified 1636-fold with a yield of 35%. Purity of the enzyme was checked by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Activity of the enzyme was determined spectrophotometrically at 340 nm and in vitro effects of ofloxacin, levofloxacin, cefazolin, and cefepime were determined. The antibiotics used in this study showed inhibitory effects on the enzyme. Concentrations of inhibitors producing 50% inhibition (I_{50}) and their inhibition constants (K_i) were estimated to be 0.159 mM and 0.5840 ± 0.3121 mM for ofloxacin, 0.090 mM and 0.3833 ± 0.2725 mM for levofloxacin, 14.871 mM and 34.5002 ± 4.2628 mM for cefazolin, and 4.589 mM and 4.9504 ± 3.8928 mM for cefepime, by using activity-[Drug] and Lineweaver-Burk graphs. Of these 4 antibiotics, ofloxacin, levofloxacin, and cefazolin were non-competitive inhibitors, whereas, cefepime was a competitive inhibitor for the enzyme. Therefore, when these drugs are given to chickens, their dosages should be carefully controlled in order to prevent their adverse effects.

Keywords: Glutathione reductase, chicken, liver, ofloxacin, levofloxacin, cefazolin, cefepime

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