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Fig. 8. NO donor, cGMP, or catalase block IGF-I-induced tyrosine phosphorylation of IGF-I receptor (IGF-IR). Cells were pretreated with 30 µM DETANO for 30 min, 30 µM 8-p-CPT-cGMP for 10 min, or 0.3 µM catalase for 180 min, followed by treatment with 3.3 nM IGF-I for 5 min. IGF-IR was then immunoprecipitated and the levels of phosphotyrosine and IGF-IR were determined by sequential Western blot analyses. A: the top blot shows phosphotyrosine levels in receptor protein, whereas the bottom blot shows IGF-I receptor protein levels, via reprobe of the blot shown at top. B: quantitative summary of four Western blot experiments. Results are given as the ratio of phosphotyrosine to IGF-IR levels (means ± SE). *P < 0.05 compared with control.
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