RESUMO
The effects on intimal hyperplasia of tissue plasminogen activator (tPA) and heparin following vascular injury were investigated. A common iliac artery in 34 hereditary hypercholesterolemic rabbits was injured by three successive 60-second balloon inflations to a pressure of 6 atm. Thereafter, two groups were continuously infused with tPA for 7 days at rates of 2 mg/kg per 24 hours (tPA-H) or 0.6 mg/kg per 24 hours (tPA-L), and two groups received intraarterial infusions of 750 U/kg (heparin-H) or 150 U/kg (heparin-L) heparin, followed by 625 U/kg or 125 U/kg subcutaneously twice daily for the same period, respectively. Twenty-eight days after injury, the intimal areas of the tPA-H (0.07 +/- 0.13 mm2), tPA-L (0.11 +/- 0.08 mm2), heparin-H (0.17 +/- 0.08 mm2), and heparin-L (0.28 +/- 0.27 mm2) groups were all significantly (P < 0.01) smaller than the controls (0.57 +/- 0.23 mm2), as were the intimal/medial cross-sectional area ratios (0.10 +/- 0.14, 0.21 +/- 0.20, 0.28 +/- 0.10, and 0.50 +/- 0.54 vs 1.13 +/- 0.74, respectively). Thus, attenuation of platelet aggregation by tPA or heparin inhibited medial smooth muscle cell proliferation and intimal hyperplasia in balloon injured arteries.
