Fig. 6.

H₂O₂ suppresses IP₃ receptor activity. (A) Representative image showing endothelial cells of an intact artery. The red circle demarks the area that was selected for photolysis of caged IP₃. Scale bar: 20 μM. (B) Heat map of Ca²⁺ signalling stimulated by photolysis of caged IP₃ in the preselected area. (C) Uncaging IP₃-evoked Ca²⁺ signalling traces of two representative single cells (cell 1 and cell 2 from B) before and after 20 min incubation of H₂O₂ (100 μM). As with ACh there was heterogeneity in the responses of cells to H₂O₂. The peak value of the Ca²⁺ signal was either unaltered (cell 2) or suppressed (cell 1) by H₂O₂. (D) Summary data showing the Ca²⁺ signal peak after uncaging. Control: blue; H₂O₂ (100 μM): red (n = 5). (E) Averaged peak value of Ca²⁺ signals from five different experiments. Control: blue; H₂O₂ treated: red, (n = 5; *p < 0.05).