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Mesenteric small artery changes after vasoconstrictor infusion in young rats
H C Boonen1, M J Daemen, P H Eerdmans
1Department of Pharmacology, University of Limburg, Maastricht, The Netherlands.
Journal of Cardiovascular Pharmacology
|September 1, 1993
Summary
Angiotensin II (AII) causes small artery hypertrophy in young rats, while chronic alpha-1 adrenergic stimulation reduces arterial smooth muscle reactivity without altering structure. Neither increased blood pressure nor vasoconstriction were involved in AII-induced hypertrophy.
Area of Science:
- Cardiovascular Physiology
- Vascular Biology
- Pharmacology
Background:
- Understanding the structural and functional adaptations of resistance arteries is crucial for comprehending hypertension.
- Chronic stimulation of alpha 1-adrenergic receptors or angiotensin II (AII) may influence vascular remodeling.
- The role of elevated blood pressure (BP) versus direct vasoactive agent effects on arterial structure needs clarification.
Purpose of the Study:
- To investigate the effects of chronic alpha 1-adrenergic stimulation, AII infusion, and elevated BP on small resistance artery structure and function.
- To differentiate the vascular remodeling effects of AII and alpha 1-adrenergic stimulation.
- To assess changes in arterial media thickness, lumen diameter, stiffness, and contractile/relaxing responses.
Main Methods:
- Mesenteric small arteries (MrA) were isolated from young Wistar Kyoto rats infused with saline, phenylephrine (alpha 1-adrenergic agonist), or AII.
- Arteries from spontaneously hypertensive rats (SHR) were also studied for comparison.
- Vascular structure (media cross-sectional area, media thickness, lumen diameter) and function (contractile and relaxing responses, stiffness) were assessed.
Main Results:
- AII infusion led to significant small artery hypertrophy (increased media cross-sectional area and thickness) without altering stiffness or lumen diameter.
- Chronic alpha 1-adrenergic stimulation did not change small artery structure but reduced maximal contractile responses and sensitivity to vasoconstrictors.
- Elevated systolic blood pressure (SBP) was observed in AII-infused rats, phenylephrine-infused rats, and SHR, but did not correlate with AII-induced hypertrophy.
Conclusions:
- Angiotensin II induces small artery hypertrophy in young rats, independent of increased blood pressure or vasoconstriction.
- Chronic alpha 1-adrenergic stimulation causes a nonselective reduction in arterial smooth muscle contractile reactivity without structural changes.
- These findings highlight distinct vascular remodeling pathways mediated by AII and alpha 1-adrenergic signaling.