Objective: Smooth muscle cell proliferation and migration are the predominant responses to intimal and medial injury after percutaneous transluminal coronary angioplasty. The in vivo inhibitory effect of heparin on these responses is well documented. To test the hypothesis that the antiproliferative effect of heparin in vivo may be related to an inhibition of proto-oncogene expression, the effects of pretreatment with heparin on the expression of the c-myc, c-fos and c-jun proto-oncogenes were examined in a rabbit model of balloon denudation.
Methods: Animals were randomised 5 h before balloon denudation to receive a subcutaneous injection of unfractionated heparin (7500 IU.kg-1, n = 7) or saline (n = 6). Total RNA extracted from the aorta 1 h after balloon denudation was analysed by northern blot technique. A histological study was also performed in saline treated (n = 4) and heparin treated (n = 4) animals 28 d after balloon denudation.
Results: The histological study showed that the degree of neointimal thickening was significantly less in heparin treated animals. However, the level of expression of the proto-oncogenes we studied was similar in both groups.
Conclusions: Heparin inhibits neointimal thickening after balloon denudation. This inhibition is not associated with an overall decrease in the level of expression of the c-myc, c-fos, or c-jun proto-oncogenes in the arterial wall, suggesting that the antiproliferative effect of heparin may be due to an effect on other events in the cell cycle.