['C-type natriuretic peptide (CNP), which is produced by vascular endothelial cells, exhibits anti-proliferative and anti-inflammatory effects. Cytotoxic T-lymphocytes may be involved in vein graft disease. Attenuation of vein graft disease necessitates a remodelling of the arterialized vein towards a more contractile phenotype which is characterized, among other factors, by the calponin amount. We investigated the effects of perivascularly applied CNP in a mouse model of vein graft disease.', 'C57BL6J mice underwent interposition of the inferior vena cava from isogenic donor mice into the common carotid artery using a previously described cuff technique. In the treatment group, 10(-6)mol/l of CNP were applied locally in pluronic gel. The control group did not receive local treatment. Grafts were harvested at 1, 2, 4, and 8 weeks and underwent morphometric analysis as well as immunohistochemical analysis.', 'In grafted veins without treatment (controls) median intimal thickness was 10 (6-29), 12 (8-40)microm, was 47 (12-58), and 79 (62-146)microm after 1, 2, 4 and 8 weeks, respectively. In the treatment groups, which received 10(-6)mol/l of CNP, the intimal thickness was 5 (3-6), 6 (4-15), 32 (5-54), and 43 (39-70)microm after 1, 2, 4 and 8 weeks, respectively. This reduction of intimal thickness was significant at 1, 2 and 8 weeks. Immunohistochemically, the reduction of intimal thickness was associated with a decreased infiltration of CD-8 positive cells and an increased amount of calponin in the CNP-treated grafts.'] Does perivascular application of C-type natriuretic peptide attenuate neointimal hyperplasia in experimental vein grafts?