Endothelin-1-induced vasopressor responses in essential hypertension

Area of Science:

• Cardiovascular Physiology
• Renal Physiology
• Pharmacology

Background:

• The role of endothelin-1 (ET-1) in human essential hypertension remains debated.
• Previous research indicated ET-1's potential in sodium retention and renal vasoconstriction.
• ET-1 also possesses mitogenic properties relevant to hypertension pathophysiology.

Purpose of the Study:

• To investigate the constrictor actions of ET-1 in essential hypertension.
• To determine if enalapril or nifedipine can modulate ET-1's systemic and renal effects.
• To assess ET-1's impact on blood pressure, cardiac index, vascular resistance, and sodium excretion.

Main Methods:

• Systemic infusion of ET-1 in nine essential hypertensive subjects at increasing doses.
• Administration of enalapril (20 mg BID) or nifedipine (60 mg OD) prior to ET-1 challenge.
• Measurement of plasma ET-1, blood pressure, cardiac index, systemic vascular resistance, renal blood flow, renal vascular resistance, and sodium excretion.

Main Results:

• ET-1 infusion significantly increased plasma ET-1, blood pressure, and systemic vascular resistance, while decreasing cardiac index.
• Renal blood flow was reduced, and renal vascular resistance increased during ET-1 infusion.
• Both enalapril and nifedipine prevented systemic ET-1 effects; nifedipine attenuated renal vasoconstriction more effectively than enalapril.
• Neither drug altered ET-1's antinatriuretic effect, but nifedipine increased basal sodium excretion.

Conclusions:

• Essential hypertensive subjects exhibit sensitivity to ET-1's vasoconstrictor effects.
• Enalapril and nifedipine can counteract systemic ET-1 actions.
• Nifedipine demonstrates superior efficacy in mitigating the renal constrictor effects of ET-1 compared to enalapril.