Mineralocorticoids upregulate arterial contraction to epidermal growth factor

Area of Science:

• Cardiovascular Physiology
• Endocrinology
• Molecular Biology

Background:

• Epidermal growth factor (EGF) plays a role in vascular function.
• The precise mechanisms regulating EGF-mediated arterial contraction are not fully understood.
• Mineralocorticoids and elevated systolic blood pressure (SBP) are potential regulators.

Purpose of the Study:

• To investigate the role of mineralocorticoids and SBP in EGF-induced arterial contraction.
• To determine if hypertension is necessary for enhanced EGF responsiveness.
• To explore the effect of aldosterone on EGF-receptor expression.

Main Methods:

• Isolated tissue-bath experiments using endothelium-denuded thoracic aortas from WKY, SHR, L-NNA hypertensive, and DOCA salt-treated rats.
• Measurement of maximal contraction to EGF.
• In vitro incubation of aortic tissues with aldosterone and assessment of EGF-receptor mRNA expression.

Main Results:

• Maximal contraction to EGF was significantly greater in hypertensive rat models (L-NNA and SHR) compared to normotensive controls (sham and WKY).
• Arteries from mildly hypertensive Wistar-Furth rats (DOCA salt) showed enhanced EGF contraction, similar to Wistar rats with higher SBP.
• Aldosterone treatment in vitro increased EGF-receptor mRNA expression in aortic tissues.

Conclusions:

• Arterial contraction to EGF can be stimulated by mineralocorticoids, potentially independent of hypertension.
• Mineralocorticoids may enhance vascular responsiveness to EGF by upregulating EGF-receptor expression.
• These findings suggest a novel role for mineralocorticoids in regulating vascular contractility.