Effects of selected endothelium-dependent vasodilators on fetoplacental vasculature: physiological implications.
The endothelium-dependent vasodilators ACh, histamine, and bradykinin were studied in the isolated, perfused human placental cotyledon. Histamine caused a decrease in perfusion pressure that was attenuated by cimetidine. Bradykinin, at lower concentrations (10(-20) to 10(-14) M), produced a concentration-dependent decrease in perfusion pressure, whereas at higher concentrations it produced an increase in perfusion pressure. ACh was without any effect. The decrease in perfusion pressure observed with bradykinin was potentiated by captopril and was significantly attenuated in the presence of HOE-140, the B(2)-receptor antagonist, or by pretreatment with an inhibitor of nitric oxide synthase, but not by an inhibitor of cyclooxygenase. The decrease in perfusion pressure observed with bradykinin was potentiated by ANG I but not by ANG II. It is concluded that endothelium-dependent vasodilation can be demonstrated with histamine and bradykinin in the fetoplacental vessels, and at least for bradykinin, this is partly mediated by release of nitric oxide. The potentiation of the bradykinin response in the presence of ANG I may serve to buffer the vasoconstriction produced by ANG II in the fetoplacental circulation.
Amarnani
S
S
Departments of Obstetrics and Gynecology and of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA.
Sangrat
B
B
Chaudhuri
G
G
D000109:Acetylcholine / Q000494:pharmacology; D001808:Blood Vessels / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005333:Fetus / Q000098:blood supply*; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052250:Nitric Oxide Synthase Type III; D009994:Osmolar Concentration; D010477:Perfusion; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D011312:Pressure; D014655:Vascular Resistance / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D006632:Histamine; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D000109:Acetylcholine; D001920:Bradykinin; D019331:NG-Nitroarginine Methyl Ester