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The H 2 O 2 ‐Generating Enzyme, Xanthine Oxidase, Decreases Luminal Ca 2+ Content of the IP 3 ‐Sensitive Ca 2+ Store in Vascular Endothelial Cells
Author(s) -
WESSON DONALD E.,
ELLIOTT STEPHEN J.
Publication year - 1995
Publication title -
microcirculation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.793
H-Index - 83
eISSN - 1549-8719
pISSN - 1073-9688
DOI - 10.3109/10739689509146767
Subject(s) - xanthine oxidase , chemistry , xanthine , inositol , calcium , thapsigargin , enzyme , extracellular , incubation , biochemistry , biophysics , receptor , biology , organic chemistry
Objective: Xanthine oxidase inhibits agonist‐stimulated Ca 2+ signaling in calf pulmonary artery endothelial cells by an H 2 O 2 ‐dependent mechanism. We investigated the effect of xanthine oxidase on luminal Ca 2+ content of the inositol‐1,4,5‐trisphosphate (IP 3 )‐sensitive Ca 2+ store. Methods: Luminal Ca 2+ content was estimated from the net release of Ca 2+ activated by 2,5‐di‐ t ‐butylhydroquinone (BHQ), an inhibitor of microsomal Ca 2+ pumps. Results: Initially, xanthine oxidase depleted the IP 3 ‐sensitive Ca 2+ store of releasable Ca 2+ , but with more prolonged incubation, the enzyme also depleted non‐IP 3 ‐sensitive stores. In addition, xanthine oxidase inhibited capacitative Ca 2+ influx. Similar results were observed when thapsigargin was substituted for BHQ. Conclusions: Depletion of luminal Ca 2+ content within the IP 3 ‐sensitive Ca 2+ store contributes to xanthine oxidase inhibition of Ca 2+ signaling in vascular endothelial cells.