Xanthine oxidase inhibits transmembrane signal transduction in vascular endothelial cells

J Pharmacol Exp Ther. 1994 Sep;270(3):1197-207.


The effect of xanthine oxidase (XO)-mediated oxidant stress on endothelial cell signal transduction was determined in bradykinin-stimulated cells loaded with the Ca+(+)-sensitive probe fura-2. Calf pulmonary artery endothelial cells were incubated with a reaction mixture containing XO (50 mU/ml) and its substrate, hypoxanthine (HX) (0.5 mM), for periods of 0.5 to 2.0 hr. HX/XO time dependently increased basal cytosolic free Ca++ ([Ca++]i) and decreased the response of [Ca++]i to bradykinin, so that incubation of cells with HX/XO for 1.5 hr or longer eliminated responsiveness to agonist. In presence of XO, HX dose dependently increased basal [Ca++]i (EC50 approximately 3 x 10(-5) M) and decreased the response of [Ca++]i to bradykinin. Sequential application of bradykinin and Ca++ to cells suspended in Ca+(+)-free/EGTA buffer was performed to characterize the effects of HX/XO on receptor-activated Ca++ entry and release of Ca++ from internal stores. HX/XO attenuated internal store Ca++ release and inhibited the bradykinin-stimulated Ca++ influx pathway in a time-dependent manner. When the HX dose was decreased by an order of magnitude, HX/XO selectively inhibited the agonist-stimulated influx pathway with little effect on internal store Ca++ release. Coincubation with superoxide dismutase tended to potentiate the effects of HX/XO, whereas catalase provided almost complete protection. Similar results to HX/XO-induced alterations in Ca++ signaling were observed when glucose-glucose oxidase (G/GO) was used as the oxidant-generating system. Inhibition of Ca++ signaling by HX/XO and G/GO occurred in the absence of decreased cell viability. Together, these results suggest that HX/XO-induced inhibition of signal transduction in endothelial cells is a function of H2O2-mediated oxidant stress and represents an early dysfunction in the process of oxidant injury.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bradykinin / pharmacology
  • Buffers
  • Calcium / metabolism
  • Catalase / pharmacology
  • Cattle
  • Cell Membrane
  • Cells, Cultured
  • Egtazic Acid
  • Endothelium, Vascular / drug effects*
  • Endothelium, Vascular / metabolism
  • Glucose Oxidase / pharmacology
  • Hydrogen Peroxide / metabolism
  • Hypoxanthine
  • Hypoxanthines / pharmacology
  • Pulmonary Artery / drug effects
  • Pulmonary Artery / metabolism
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / drug effects*
  • Superoxide Dismutase / pharmacology
  • Xanthine Oxidase / pharmacology*


  • Buffers
  • Hypoxanthines
  • Reactive Oxygen Species
  • Hypoxanthine
  • Egtazic Acid
  • Hydrogen Peroxide
  • Glucose Oxidase
  • Catalase
  • Superoxide Dismutase
  • Xanthine Oxidase
  • Bradykinin
  • Calcium