Analysis of Mechanisms for Increased Blood Pressure Variability in Rats Continuously Infused with Angiotensin II

Area of Science:

• Cardiovascular Physiology
• Hypertension Research
• Pharmacology

Background:

• Angiotensin II (Ang II) infusion in rats serves as a model for hypertension and elevated 24-hour blood pressure variability (BPV).
• Understanding the underlying mechanisms of Ang II-induced BPV is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the mechanisms responsible for Ang II-induced BPV.
• To evaluate the impact of Ang II on blood pressure (BP), heart rate (HR), baroreceptor reflex sensitivity (BRS), and aortic arch medial thickness.
• To assess the protective effects of azelnidipine against Ang II-induced alterations.

Main Methods:

• Continuous subcutaneous infusion of Ang II (5.2 μg/kg/h) in Wistar rats for 14 days.
• Co-administration of azelnidipine (30 mg/kg/day) in a subset of rats.
• Radiotelemetry for continuous BP and HR monitoring; BPV assessed by standard deviation.
• BRS quantified via sequence analysis; aortic arch medial thickness measured microscopically.

Main Results:

• Ang II infusion significantly increased BPV at days 7 and 14.
• The correlation between BP and HR shifted from positive to negative and then diminished.
• BRS was impaired, and aortic arch medial thickness increased in Ang II-infused rats.
• Azelnidipine administration attenuated all observed Ang II-induced changes.

Conclusions:

• Continuous Ang II infusion over 14 days induces sequential changes in the mechanisms underlying augmented BPV.
• These changes involve alterations in autonomic regulation and aortic structure.
• Azelnidipine demonstrates a protective effect against Ang II-induced cardiovascular dysregulation.