IGF1 and hyperinsulinemic hypoglycemia, familial, 4: To elucidate the likely mechanism contributing to the exacerbation of hypertension‐induced MMP activation in IGF‐1 deficiency, we compared pressure‐induced production of O2·− in cerebral arteries isolated from IGF‐1‐deficient mice and their respective age‐matched controls using the redox‐sensitive dye dihydroethidium (DHE).