Vasopeptidase inhibition has potent effects on blood pressure and resistance arteries in stroke-prone spontaneously hypertensive rats

Abstract

The antihypertensive agent omapatrilat represents a novel approach to antihypertensive therapy, namely vasopeptidase inhibition. Omapatrilat (BMS- 186716) concomitantly inhibits neutral endopeptidase and angiotensin- converting enzyme, leading to protection from degradation of natriuretic and other hypotensive peptides in addition to interruption of the renin- angiotensin system. Although the potency of omapatrilat on reduction of blood pressure has been reported, its effects on resistance artery structure and function were unknown. We tested omapatrilat in stroke-prone spontaneously hypertensive rats (SHRSP), a malignant model of hypertension, with the hypothesis that it would improve the structure and endothelial function of mesenteric resistance arteries. Ten-week-old SHRSP were treated orally for 10 weeks with omapatrilat (40 mg/kg per day). Mesenteric arteries (lumen <300 μm) were studied on a pressurized myograph. After 10 weeks, untreated SHRSP had a systolic blood pressure of 230±2 mm Hg that was significantly reduced (P<0.05) by omapatrilat (145±3 mm Hg). Omapatrilat treatment improved endothelium-dependent relaxation of resistance arteries as elicited by acetylcholine (10-5 mol/L) but had no significant effect on endothelium- independent relaxation produced by a nitric oxide donor (sodium nitroprusside). This suggested that there existed endothelial dysfunction in SHRSP that was corrected by vasopeptidase inhibition, probably in part caused by the potent blood pressure-lowering effect of omapatrilat. Media width and media/lumen ratio were significantly decreased (P<0.05) by omapatrilat, and a trend (P=0.07) to increase lumen diameter was observed. Vascular stiffness (slope of the elastic modulus versus stress curve) was unaltered by omapatrilat. In conclusion, omapatrilat, acting as a potent antihypertensive agent, may improve structure and endothelial function of resistance arteries in SHRSP, a severe form of genetic hypertension.