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Bradykinin-induced vasoconstriction and thromboxane release in perfused human placenta
1Department of Medicine, North Shore University Hospital, Manhasset, New York.
The American Journal of Physiology
|June 1, 1988
Summary
Bradykinin constricts human fetoplacental circulation by increasing thromboxane production. This study reveals thromboxane as a key mediator in this vasoconstrictive response, impacting placental blood flow.
Area of Science:
- Reproductive biology
- Vascular physiology
- Pharmacology
Background:
- Bradykinin typically acts as a vasodilator.
- Its vasoconstrictive effect in the human fetoplacental circulation is not well understood.
- Potential interactions with other pressor systems were investigated.
Purpose of the Study:
- To investigate the effects of bradykinin on human fetoplacental circulation.
- To determine the mechanisms underlying bradykinin-induced vasoconstriction.
- To elucidate the role of thromboxane and angiotensin II in this response.
Main Methods:
- Perfusion of a single human placental cotyledon artery with RPMI medium.
- Administration of bradykinin and a thromboxane agonist.
- Measurement of perfusion pressure and levels of thromboxane B2 and prostaglandin E2.
- Use of specific antagonists: saralasin (angiotensin II antagonist) and SQ29548 (thromboxane antagonist).
Main Results:
- Bradykinin caused a dose-related increase in vascular resistance.
- Bradykinin significantly increased thromboxane B2 (62.0%) and prostaglandin E2 (86.7%) production.
- Thromboxane antagonism (SQ29548) inhibited the bradykinin pressor response by 61.6%.
- Angiotensin II did not mediate the bradykinin response.
Conclusions:
- Thromboxane is a critical mediator of bradykinin-induced vasoconstriction in the human placenta.
- Bradykinin's pressor effects in this vascular bed are primarily mediated through thromboxane pathways.
- Understanding these mechanisms is vital for managing fetoplacental circulatory disorders.