Fig. 5.

Effects of oxidative stress on the tertiary arterioles of the retinal microvasculature. A: arteriolar cell death induced by 15 μM H₂O₂ under various experimental conditions. 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, in solution A lacking added calcium, or in solution A plus 10 μM nifedipine. For each group, 8 ± 2 microvessel-containing coverslips were assayed. H₂O₂-induced arteriolar cell death was significantly (*P < 0.001) less in the H₂O₂/glibenclamide and H₂O₂/low calcium groups. Nifedipine did not significantly affect H₂O₂-induced arteriolar cell death. B: time course for the change in the intracellular calcium concentration of tertiary arteriolar cells during exposure to solution A supplemented with 15 μM H₂O₂ in the absence (n = 24) or presence of 0.5 μM glibenclamide (n = 25). C: effect of extracellular calcium, SKF-96365, and nifedipine on the H₂O₂-induced increase in the intracellular calcium concentration of arteriolar mural cells. For the H₂O₂ group, microvessels were exposed to solution A without additives followed by exposure to solution A plus 15 μM H₂O₂ for 400 s. For the H₂O₂/low calcium group, microvessels were initially monitored in solution A without added calcium prior to the addition of 15 μM H₂O₂. For the H₂O₂/SKF-96365 group, microvessels were perfused with solution A supplemented with 50 μM SKF-96365 before the addition of 15 μM H₂O₂. For the H₂O₂/nifedipine group, microvessels were perfused with solution A supplemented with 10 μM nifedipine prior to the addition of 15 μM H₂O₂. For each group, 63 ± 21 ROIs were monitored. The increase in calcium was determined as noted in the legend of Fig. 3 and detailed in materials and methods. The H₂O₂-induced increase in mural cell calcium was significantly (*P < 0.001) less in the H₂O₂/low calcium and H₂O₂/SKF-96365 groups; nifedipine significantly (*P < 0.001) increased the H₂O₂-induced increase in mural cell calcium.