FUNCTIONAL EVIDENCE THAT BALLOON ANGIOPLASTY RESULTS IN TRANSIENT NITRIC-OXIDE SYNTHASE INDUCTION

Since serious vasospastic episodes limit the efficacy of percutaneous transluminal coronary angioplasty, this study has examined the time-de pendent changes in vascular reactivity that occur following rat caroti d artery balloon angioplasty. Relative to vessels from sham-operated a nimals, angioplasty caused an immediate increase in endothelin-1 contr actile potency, an observation not made with noradrenaline or KCl, imp licating endothelin-1 in the pathogenesis of acute arterial vasospasm. This hyperreactivity, possibly resulting from the loss of endothelin- 1-induced nitric oxide release from the endothelium, was transient and was followed by a non-specific decrease in reactivity to all three sp asmogens. Since the delayed reduction in endothelin-1 contractile pote ncy was restored by N omega-nitro-L-arginine methyl ester, this hypore activity appeared to result from nitric oxide synthase induction. Furt hermore, since the regenerating endothelium was dysfunctional, the gen eration of nitric oxide was from a non-endothelial source (possibly th e smooth muscle or infiltrating macrophages). This response may functi on to ameliorate the spasmogenic and proliferative actions of chronica lly acting vasoactive factors and oppose platelet aggregation.