Bradykinin-induced vasoconstriction and thromboxane release in perfused human placenta.
This investigation was performed to study the effects of bradykinin on the human fetoplacental circulation. The artery to a single placental cotyledon was perfused with RPMI medium (0.764 ml/min). Bradykinin caused a dose-related increase in vascular resistance. Because bradykinin is generally a vasodilator, we investigated the possibility that bradykinin-induced vasoconstriction was due to interactions with other pressor systems. Bradykinin and 9,11-dideoxy-9 alpha, 11 alpha-epoxymethanoprostaglandin F2 alpha (a stable thromboxane agonist) caused a dose-related increase in perfusion pressure. The bradykinin response was not mediated by angiotensin II, because bradykinin-induced vasoconstriction was not inhibited by saralasin, a competitive angiotensin antagonist. Bradykinin increased thromboxane B2 production by 62.0%. Prostaglandin E2 levels were increased by 86.7%, but prostaglandin E2 did not affect fetoplacental vascular resistance. Angiotensin II did not stimulate thromboxane B2 production and caused only a slight increase in prostaglandin E2. Indomethacin decreased the pressor response to angiotensin II. SQ29548, a specific thromboxane antagonist, caused a 61.6% inhibition of the bradykinin pressor response but did not change angiotensin II responsiveness. The data demonstrate that thromboxane is an important mediator of bradykinin-induced vasoconstriction in the isolated perfused human placenta.
Wilkes
B M
BM
Department of Medicine, North Shore University Hospital, Manhasset, New York.
Mento
P F
PF
D000804:Angiotensin II / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004305:Dose-Response Relationship, Drug; D005231:Fatty Acids, Unsaturated; D005260:Female; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D009924:Organ Culture Techniques; D010920:Placenta / Q000098:blood supply* / Q000378:metabolism; D011247:Pregnancy; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D013928:Thromboxane A2 / Q000037:antagonists & inhibitors; D013929:Thromboxane B2 / Q000378:metabolism*; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects*
D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D011450:Prostaglandin Endoperoxides, Synthetic; D000804:Angiotensin II; D013929:Thromboxane B2; C028429:U 44069; D013928:Thromboxane A2; C045749:SQ 29548; D001920:Bradykinin; D007213:Indomethacin