Fig. 2.

K_ATP channel activation in retinal microvessels during exposure to H₂O₂. A: time course for the hyperpolarizing effect of 15 μM H₂O₂. Values are the means of 4 experiments. During H₂O₂ exposure, the membrane potential increased significantly (P < 0.001). B: during continuous recordings (n = 4), current-voltage (I-V) plots were generated during exposure of the retinal microvascular complex to solution A (control, ■), 9 ± 2 min after the onset of exposure to solution A supplemented with 15 μM H₂O₂ (●), and finally 11 ± 2 min after the addition of 0.5 μM glibenclamide to the H₂O₂-containing solution (○). Exposure to H₂O₂ significantly (P = 0.001, paired t-test) increased the ionic conductance; glibenclamide significantly (P = 0.001, paired t-test) decreased the H₂O₂-induced conductance. Inset: I-V relations of the H₂O₂-induced conductance, which is the difference between the control and H₂O₂ I-V plots shown in this panel. C: effect of glibenclamide and low extracellular calcium on H₂O₂-induced capillary cell death. Microvessels were exposed for 6 h to 15 μM H₂O₂ in solution A without additives (H₂O₂ group), in solution A with 0.5 μM glibenclamide, or in solution A lacking added calcium. For the H₂O₂, H₂O₂/glibenclamide, and H₂O₂/low calcium groups, 14, 5, and 6 microvessel-containing coverslips were assayed, respectively. H₂O₂-induced capillary cell death was significantly (*P < 0.001) less in the glibenclamide and low calcium groups.