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Vasoconstriction is amplified by autoregulation during vasoconstrictor-induced hypertension
G A Meininger1, J P Trzeciakowski
1Microcirculation Research Institute, College of Medicine, Texas A&M University, College Station 77843.
The American Journal of Physiology
|April 1, 1988
Summary
Systemic vasoconstrictors like angiotensin II and phenylephrine stimulate blood flow autoregulation. This interaction amplifies vascular resistance, particularly at lower vasoconstrictor doses.
Area of Science:
- Physiology
- Cardiovascular Research
- Pharmacology
Background:
- Vascular resistance is determined by blood flow autoregulation and vasoconstrictor agents.
- Understanding this interaction is crucial for managing blood pressure and circulation.
Purpose of the Study:
- To investigate how blood flow autoregulation interacts with vasoconstrictors.
- To determine the combined effect on vascular resistance.
Main Methods:
- Rats were instrumented to measure superior mesenteric artery blood flow and calculate vascular resistance.
- An adjustable occluder controlled local perfusion pressure independently of mean arterial pressure (MAP).
- Infusions of angiotensin II and phenylephrine were administered at various doses.
Main Results:
- Angiotensin II caused a dose-dependent shift in the pressure-flow relationship and increased MAP.
- Low-dose phenylephrine increased MAP but did not shift the pressure-flow curve; higher doses did.
- When MAP rose, autoregulation amplified vascular resistance, especially at low phenylephrine doses.
Conclusions:
- Elevated mean arterial pressure during vasoconstrictor infusion stimulates autoregulation.
- Autoregulation amplifies the local increase in vascular resistance induced by vasoconstrictors.
- The rise in MAP contributes significantly to increased vascular resistance, independent of direct vasoconstrictor effects at low doses.