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

•Effect of GHRH and GRP antagonism on arterial intimal hyperplasia in diabetic rats.•Reduced vascular smooth muscle growth after GHRH and GRP antagonism in vitro.•GHRH antagonism reduced arterial intima to media ratio and % area stenosis in vivo.

IntroductionArterial 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.MethodsTwo 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.ResultsIn 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).ConclusionsThe 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.