Mesenteric artery contraction and relaxation studies using automated wire myography

Area of Science:

• Cardiovascular Physiology
• Vascular Biology
• Renal Physiology

Background:

• Proximal resistance vessels, like mesenteric arteries, are crucial for regulating peripheral resistance and blood flow distribution.
• The calcium-sensing receptor (CaR) on perivascular nerves mediates vasorelaxation in response to extracellular calcium.
• Hypertension is often associated with altered vascular reactivity and impaired vasodilation.

Purpose of the Study:

• To investigate the role of the CaR in mediating extracellular calcium-induced relaxation of rat mesenteric arteries.
• To compare the vascular response to calcium in Wistar, Dahl salt-sensitive (DS), and Dahl salt-resistant (DR) rats.
• To determine if CaR expression or function is altered in Dahl rat models of hypertension.

Main Methods:

• Utilized automated wire myography to assess isometric tension and contractile responses of isolated rat mesenteric arteries.
• Measured agonist-induced contractions and subsequent relaxation upon cumulative addition of extracellular calcium ([Ca2+]e).
• Quantified CaR expression in mesenteric arteries from different rat strains.

Main Results:

• Wistar rat mesenteric arteries exhibited higher calcium sensitivity compared to DR and DS rats.
• DS rat mesenteric arteries showed reduced CaR expression, correlating with diminished [Ca2+]e-induced relaxation.
• Dahl rats, particularly DS rats, possess an inherent defect in the CaR signaling pathway affecting vasorelaxation.

Conclusions:

• The CaR is essential for mesenteric artery relaxation under conditions of increased adrenergic tone, relevant to hypertension.
• Dahl rats exhibit impaired CaR-mediated vasorelaxation, suggesting a defect in this signaling pathway.
• This defect is more pronounced in DS rats, highlighting its contribution to salt-sensitive hypertension.