The Role of Cellular Glutathione Redox Cycle and Glutathione in the Regulation of Ileum Contractility.

Redox homeostasis is driven by the ratio of the concentrations of cellular redox couples. The aim of this study was to reduce 2GSH/GSSG turnover in an ex vivo ileum by the irreversible inhibition of glutathione reductase (GR) activity (by BCNU) and evaluate its effects on contractility, antioxidant enzyme activity, and thiol levels. Increasing concentrations of BCNU as well as a single EC50 BCNU dose significantly reduced both contraction amplitude and GR activity. The addition of cumulative doses of both GSH and GSSG after EC50 BCNU caused further dose-dependent amplitude reduction, but turned GR activity to control levels and reduced CuZn-superoxide dismutase activity; cumulative doses of GSH also decreased catalase activity. Both GSH and GSSG cumulative doses decreased the contractility of non-treated control ileum in a dose-dependent manner, while GSH also increased glutathione peroxidase (GPx) activity. The correlation analysis showed a negative relationship between contractility and non-protein thiols, and positive correlations between catalase and GPx activities in BCNU treated ileum, as well as between GPx and non-protein thiols in solvent controls. The results present a framework for how glutathione turnover and ileum contractility are linked.