Inhibition of endothelin-converting enzyme for protection against neointimal proliferation following balloon angioplasty of the rat carotid artery.

Clinical success of percutaneous transluminal coronary angioplasty is limited by restenosis within months of the initial intervention. A number of vasoactive mediators and growth factors have been reported to participate in this process. The aim of the present experiments was to examine the effects of nonselective neutral endopeptidase (NEPi)/endothelin-converting enzyme (ECEi) inhibitors against neointimal proliferation (NIP) following balloon angioplasty of the left carotid artery of Sprague-Dawley rats with the right vessel serving as the uninjured control. The rats were divided in several groups: group 1, nontreated (vehicle); group 2, treated with a selective NEPi i.p.; groups 3-7, treated with nonselective NEPi/ECEi either i.p., s.c., i.v., or p.o. at various doses. After 2 weeks, cross-sectional histopathological and morphometrical examination of the left carotids revealed a severe NIP in vehicle-treated angioplastic rats compared with the control uninjured right carotid of the same rats. The selective NEPi CGS 24592 had no significant effect on restenosis, nor did the dual NEPi/ECEi CGS 26303 at 5 mg x kg(-1) x day(-1) i.p. Both s.c and i.v. NEPi/ECEi treatment (10 mg x kg(-1) x day(-1) b.i.d. s.c. or 10 mg x kg(-1) x day(-1) i.v.) reduced NIP by up to 35%. The prodrug CGS 26393 (p.o.) also attenuated NIP by 23%. Plasma concentrations of these compounds correlated with the degree of inhibition. These data support the participation of the endothelin system in the rat model of balloon angioplasty and suggest that selective ECEi may be effective.