Apparent racial difference in response to angiotensin I infusion

Area of Science:

• Cardiovascular Research
• Pharmacology
• Human Physiology

Background:

• The renin-angiotensin-aldosterone system (RAAS) plays a critical role in blood pressure regulation.
• Individual variability in response to vasoactive substances like angiotensin I is significant.
• Understanding ethnic differences in RAAS activity is important for personalized medicine.

Purpose of the Study:

• To investigate ethnic differences in angiotensin I sensitivity between Black and White volunteers.
• To explore the relationship between angiotensin I sensitivity, plasma renin activity, and urinary sodium excretion.
• To assess the implications of these findings for the use of angiotensin I infusion as a pharmacodynamic model for ACE inhibitors.

Main Methods:

• Angiotensin I infusion in 16 healthy volunteers (8 Black, 8 White) with controlled baseline blood pressure.
• Gradual increase in infusion rate until diastolic blood pressure reached ≥95 mm Hg.
• Measurement of plasma renin activity and 24-hour urinary sodium excretion.

Main Results:

• Black volunteers required significantly lower angiotensin I infusion rates (1.8 µg/min) compared to White volunteers (3.9 µg/min) to achieve target diastolic blood pressure.
• Plasma renin activity was similar between ethnic groups.
• Black volunteers exhibited significantly higher 24-hour urinary sodium excretion (223 mmol) than White volunteers (121 mmol).

Conclusions:

• Ethnic differences in angiotensin I sensitivity exist, with Black individuals being more sensitive.
• Dietary sodium intake is a likely contributing factor to the observed differences in angiotensin I sensitivity.
• These ethnic and dietary factors must be considered when utilizing angiotensin I infusion models for studying ACE inhibitors.