Article Review: Small Arteries From Old Spontaneously Hypertensive Rats Exhibit Enhanced Endothelium-Independent Vasodilatory Capacity and Reduced Stiffness
RamÃrez-Pérez, F. I., Jurrissen, T. J., Augenreich, M. A., Castorena-González, J. A., Morales-Quinones, M., Foote, C. A., … MartÃnez-Lemus, L. A. (2025). Small arteries from old spontaneously hypertensive rats exhibit enhanced endothelium-independent vasodilatory capacity and reduced stiffness. Microcirculation, 32(2), e70004. https://doi.org/10.1111/micc.70004
System Used:
Pressure Arteriography
Purpose:
This study examines the effect of aging with hypertension on microvascular function and structure, challenging assumptions extrapolated from the large arteries.
Process:
- Compared small mesenteric arteries of aged spontaneously hypertensive rats (SHRs) with age-matched normotensive controls (WKY rats).
- Measured stiffness, dilation responses to nitric oxide donors, cytoskeletal markers like F-actin, and MMP-2 and MMP-9 levels.
- Examined human small mesenteric arteries of aged hypertensive and young normotensive patients to see if such patterns apply to human beings.
Key Findings:
- Older hypertensives in humans had stiffer small arteries and more F-actin (indicating classic vascular aging).
In rats (old SHRs), though: - Small arteries were less stiff than controls.
- They showed enhanced endothelium-independent vasodilation (to nitric oxide donors) rather than blunted dilation.
- SHR vessels’ F-actin was not increased.
- MMP-2 and MMP-9 were increased in expression; exogenous supplementation of them to normal arteries increased their dilating responses.
What it means
Instead of merely recapitulating the alterations seen in the large arteries, small resistance arteries may respond differently when both hypertension and aging co-exist. They are more flexible and more responsive to dilation.
Elevated levels of MMP are reported by the authors to enable remodeling of the vessel wall so that it becomes less stiff and more responsive.
What this does suggest is that alterations in the small vessels are not identical to those in larger arteries, and that patterns seen in large vessels do not necessarily predict how the small vessels will behave, especially when comparing different species or vessel types.
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