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Activated plasma coagulation β-Factor XII-induced vasoconstriction in rats
Peter C Papageorgiou1, Erik L Yeo, Peter H Backx
1Heart and Stroke/Richard Lewar Centre of Excellence, University of Toronto, Toronto, ON, Canada.
Clinical Science (London, England : 1979)
|January 6, 2012
Summary
The β-fragment of activated plasma coagulation Factor XII (β-FXIIa) increases blood pressure and total peripheral resistance in rats. This vasoconstrictor response involves both adrenal catecholamine-mediated and independent pathways, highlighting β-FXIIa
Area of Science:
- Physiology
- Cardiovascular Research
- Hemodynamics
Background:
- The β-fragment of activated plasma coagulation Factor XII (β-FXIIa) is known to stimulate bradykinin-mediated catecholamine release, leading to transient increases in blood pressure and heart rate in specific experimental conditions.
- Previous studies utilized anesthetized, vagotomized, ganglion-blocked, and captopril-treated rats to demonstrate the effects of β-FXIIa.
Purpose of the Study:
- To investigate the hemodynamic effects of continuous intravenous infusion of β-FXIIa in intact, untreated rats.
- To determine whether β-FXIIa elicits a vasoconstrictor response and to elucidate the role of adrenal glands in this response.
Main Methods:
- Intravenous infusion of β-FXIIa (85 ng/min per kg) or saline (control) for 60 minutes into Brown Norway rats.
- Hemodynamic parameters including mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), and left ventricular volume were continuously monitored.
- Total peripheral resistance (TPR) was calculated. Experiments were conducted in adrenally intact rats and rats after bilateral adrenalectomy (2ADX).
- Plasma concentrations of adrenaline (epinephrine) were measured at the end of the study.
Main Results:
- Saline infusion had no significant hemodynamic effects.
- In adrenally intact rats, β-FXIIa infusion increased MAP and TPR, despite decreases in SV and HR.
- In 2ADX rats, β-FXIIa infusion increased TPR but decreased MAP and SV, with no effect on HR.
- Adrenally intact rats showed persistent vasoconstriction after β-FXIIa infusion, while 2ADX rats exhibited a return to baseline TPR and a sustained decrease in MAP.
Conclusions:
- Intravenous infusion of β-FXIIa induces increases in total peripheral resistance in rats.
- The vasoconstrictor effects of β-FXIIa are mediated through both adrenal catecholamine-dependent and independent mechanisms.
- These findings suggest a complex role for β-FXIIa in regulating vascular tone and blood pressure.
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