Insights into angiotensin II receptor function through AT2 receptor knockout mice

Area of Science:

• Cardiovascular Physiology
• Renal Physiology
• Molecular Endocrinology

Background:

• Angiotensin II exerts effects through AT1 and AT2 receptors, with AT2 receptor function remaining largely unknown.
• AT2 receptor gene-deficient (AT2-/-) mice provide a model to investigate its physiological roles.
• Classical physiological techniques adapted for mice enabled detailed study of AT2 receptor function.

Purpose of the Study:

• To elucidate the physiological functions of the angiotensin II AT2 receptor.
• To characterize the cardiovascular and renal phenotype of AT2 gene-deficient mice.
• To assess the role of the AT2 receptor in hypertension and cardiac remodeling.

Main Methods:

• Comparative physiological studies of AT2-/- and wild-type (AT2+/+) mice.
• Telemetry for blood pressure monitoring and circadian rhythm analysis.
• Assessment of pressure-natriuresis, baroreflex sensitivity, cardiac function, and response to hypertensive stimuli (l-NAME, DOCA-salt).

Main Results:

• AT2-/- mice displayed a rightward shift in pressure-natriuresis, indicating impaired renal salt excretion.
• Elevated blood pressure (approx. 10 mmHg) and disturbed circadian rhythms were observed in AT2-/- mice.
• AT2-/- mice showed exacerbated cardiac hypertrophy and fibrosis in response to l-NAME-induced hypertension.

Conclusions:

• The AT2 receptor plays a crucial role in regulating blood pressure and renal function.
• AT2 receptor signaling appears to exert antiproliferative and antifibrotic effects.
• Absence of the AT2 receptor leads to increased susceptibility to hypertension and cardiac complications.