Small Arteries From Old Spontaneously Hypertensive Rats Exhibit Enhanced Endothelium-Independent Vasodilatory Capacity and Reduced Stiffness

Abstract

Objective

In conduit arteries, aging and hypertension are associated with stiffening characterized by increased cytoskeletal F-actin and endothelial dysfunction. Herein, we determined if this also happens at the level of the resistance vasculature.

Methods

We retrospectively compared the mechanical and structural characteristics of small arteries isolated from older hypertensive and younger normotensive (64.7 ± 2.8 vs. 32.1 ± 1.9 years old) human subjects. The intersection of aging and hypertension was studied in small mesenteric arteries from old (88 weeks of age) spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) normotensive rats.

Results

Arteries from older hypertensive subjects were stiffer and had more F-actin, relative to those from younger normotensives. Comparatively, arteries from old SHRs showed reduced stiffness and increased vasodilation to sodium nitroprusside without changes in F-actin. Matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) were increased in the SHR arteries and exposure of naive arteries to exogenous MMP-2 and MMP-9 augmented responsiveness to sodium nitroprusside and adenosine.

Conclusions

In conclusion, resistance arteries from old SHRs are softer and vasodilate more to exogenous nitric oxide than those of WKY rats. This improved endothelial-independent vasodilation is associated with an increased vascular expression of MMP-2 and MMP-9. We further conclude that aging and hypertension effects on the microcirculation may vary between species and vascular beds.