Effects of hydrogen peroxide on phenylephrine-induced contraction of abdominal or thoracic aorta from adult rats

Background: The effect of oxidative stress promotes activity enzymatic in vascular wall that produces hydrogen peroxide with the effect on endothelium and the development of cardiovascular diseases. Aims: We evaluated the effect of hydrogen peroxide on vascular function in thoracic and abdominal aorta. Methods: Under basal conditions, 3- and 6-month-old rats had similar blood pressure, but age- and aortic segment-dependent differences in other parameters. Results: In abdominal aorta of 6-month-old rats, superoxide dismutase activity was unchanged but there was a decrease in catalase activity, nitric oxide concentration and the phenylephrine-induced contraction. This diminished phenylephrine response was similar when adding H₂O₂, later restored by L-NAME or Wortmannin. Moreover, p-Akt expression increased in 6-month-old rats after adding H₂O₂. In thoracic aorta of 6-month-old rats, antioxidant activity increased. No differences were found in 3- or 6-month-old rats regarding the response to Ach or Phe in this aortic segment. In conclusion, in this study we found that H₂O₂ plays a key role in the modified endothelium-dependent response to phenylephrine (through PI3K/Akt/NO mechanisms) in the abdominal aorta of normotensive rats. The results were different in thoracic aorta.