Impairment of α1-adrenoceptor-mediated calcium influx in contralateral carotids following balloon injury: beneficial effect of superoxide anions.

There are many evidences indicating a compensatory mechanism in contralateral carotids following balloon injury. Previously it was observed α1-adrenoceptor-mediated hyper-reactivity and impairment of calcium influx in contralateral carotids 4 days after injury. At a later stage, α1-adrenoceptor-mediated contraction is similar to the control and we hypothesized that downstream signaling was normal. In the present study, we aimed to evaluate α1-adrenoceptor-mediated calcium influx in contralateral carotids 15 days after balloon injury. Concentration-response curves for CaCl2 in presence of the α1-adrenoceptor agonist (phenylephrine), measurement of the intracellular calcium transient and the levels of reactive oxygen species using fluorescent dyes were performed in control and contralateral carotids. Phenylephrine-induced intracellular calcium mobilization in contralateral carotids was not altered, while phenylephrine-induced calcium influx was reduced in the contralateral artery. Nitric oxide synthase inhibitors, L-NAME or L-NNA, restored this response, but nitrite and nitrate levels were decreased in contralateral carotids. Additionally, a rise in oxygen free radicals was observed in contralateral carotids. Furthermore, Tiron, a superoxide anion scavenger, restored α1-adrenoceptor-mediated calcium influx in contralateral carotids to the control level. Similar results were observed with the selective potassium channels blockers 4-aminopyridine and charybdotoxin. In conclusion, data showed that balloon catheter injury resulted in increased superoxide anions levels, activation of potassium channels (Kv and BKCa), inhibition of calcium channels (Cav) and preservation of α1-adrenoceptor-mediated contraction at a later stage after injury.