The effects of a growth hormone-releasing hormone antagonist and a gastrin-releasing peptide antagonist on intimal hyperplasia of the carotid artery after balloon injury in a diabetic rat model☆

Introduction: Arterial restenosis after angioplasty/stenting has hindered coronary artery disease treatment, especially in diabetics. We theorized that gastrin-releasing peptide (GRP) antagonists and growth hormone-releasing hormone (GHRH) antagonists might decrease neointimal hyperplasia and restenosis in diabetic rats after common carotid arterial balloon injury. Methods: Two separate experiments were conducted to test the effects of a GRP antagonist (RC-3095) and a GHRH antagonist (MZ-4-71) on vascular smooth muscle (VSM) growth. In a preliminary in vitro experiment non-injured human aortic vascular smooth muscle (VSM) proliferation was compared between growth media and control. In a second in vivo experiment, intimal and medial area, intima/media ratio (IM) and percent stenosis were compared between injured carotid arteries in twelve Zucker type II obese rats treated with subcutaneously injected RC-3095, MZ-4-71, or control media. Results: In the in vitro experiment, decreased VSM cell growth was observed in GRP antagonist (p < 0.05) and GHRH antagonist groups (p < 0.05) compared to the control group. In the in vivo experiment, the GRP antagonist group had a decreased IM ratio (1.63 ± 0.41, p < 0.05) and an increased area of stenosis (98.78% ± 1.48 p = NS) compared to control (2.38 ± 1.09) while the GHRH antagonist group had decreased IM ratio (1.33 ± 0.58 SD, p < 0.05) and percent area of stenosis (78.84% ± 24.97, p < 0.05) compared to control (2.38 ± 1.09). Conclusions: The significant decrease in both IM ratio and percent area of stenosis in the GHRH antagonist group supports the hypothesis that this peptide may reduce neointimal hyperplasia and restenosis.