Role of Angiotensin II Subtype 1 Receptor in Smooth Muscle Cells Apoptosis after Balloon Injury to Vessel

ET AL.: Role of Angiotensin II Subtype 1 Receptor in Smooth Muscle Cells Apoptosis after Balloon Injury to Vessel. In order to investigate the mechanism of smooth muscle cells apoptosis after balloon injury to vessel, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and immunohistochemistry were adopted to measure the percentage of vascular smooth muscle cell (VSMC) apoptosis and the expression of angiotensin II subtype 1 receptor (AT 1 R). Compared with sham's, the expression of AT 1 R protein in vascular media was significantly increased at 3 days after balloon injury (P<0.05), and then did not change significantly . At 7 days, it was approximately twice in intima as that in media. At 28 days it reached its peak. VSMCs apoptosis occurred in vascular media at 3 days after balloon injury and reached a peak in media and intima where apoptosis was mainly present at 7 days, then decreased. At 28 days after balloon injury, only a few apoptotic cells were in intima. AT 1 R antagonist (irbesartan) significantly increased VSMCs apoptosis. We thus conclude that AT 1 R is upregulated after balloon injury and angiotensin II inhibits VSMC apoptosis by binding to AT 1 R. (J HK Coll Cardiol 2000;8:49-57) Angiotensin II, receptor, vascular smooth muscle, apoptosis