Fig. 5.

Activation of Src kinase modulates superoxide generation and contraction of coronary artery evoked by PDBu. Inhibition of Src kinase by 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (10 μM PP2) decreased basal (A; n = 10) and PDBu-induced superoxide generation (B; n = 10) and contraction (C; n = 10). Inactive analog of PP2, PP3 (10 μM) did not decrease superoxide generation (basal: 475 ± 25; and PDBu: 3,046 ± 538 U/mg). Src kinase activation by PDBu was determined by changes in phospho-Src₄₁₆-to-total-Src ratios after immunoprecipitation. Stimulation of coronary arterial rings with PDBu (10 μM) increased Src phosphorylation in a time (0, 5, 10, and 20 min)-dependent manner (D). Pretreatment of coronary artery with peg-catalase (150 U/ml) in the presence of PDBu decreased Src kinase phosphorylation below basal levels in the absence of PDBu (E). F: summary data for the effect of peg-catalase on the PDBu-elicited increase in phospho-Src-to-total-Src ratios.