Effects of enalaprilat on neointimal growth of cultured rabbit aorta following balloon injury

Our objective was to determine if the ability of an angiotensin-converting enzyme (ACE) inhibitor to attenuate neointima formation in balloon-damaged vessel is expressed in an isolated organ culture model of neointimal growth . In vivo balloon angioplasty in combination with in vitro organ culture wa s used to produce a unique model of vascular neointima formation. Aortic se gments were cultured in medium containing a broad concentration range of th e ACE inhibitor enalaprilat (0-100 mu M). Cell proliferative indices and ne ointima:media thickness ratios were determined from vessel segments after 1 , 4, and 7 days in culture. We observed no significant effect on either par ameter at any dose of enalaprilat. Linear regression analysis on the rate o f increase in intima to media thickness ratios during the 7 days of culture also showed no effect of enalaprilat at any concentration. We conclude tha t enalaprilat has no effect on neointimal growth or cell proliferation in t his vascular organ culture model, and it is suggested that ACE inhibitors m ay act by mechanisms other than local converting enzyme inhibition to atten uate neointimal growth in rabbits following vascular ballooning in vivo.