The action of two natriuretic peptides (atrial natriuretic peptide and brain natriuretic peptide) in the human placental vasculature.
OBJECTIVE
Our purpose was to compare the actions of atrial natriuretic peptide and brain natriuretic peptide in the human placental vasculature.


METHODS
Isolated placental cotyledons were dually perfused with fetal perfusion pressure used as an index of vascular response. The effect of angiotensin II (10(-10) to 10(-6) mol/L bolus injection) was established in the absence or presence of atrial natriuretic peptide (10(-8) mol/L) or brain natriuretic peptide (10(-8) mol/L final concentration). The role of nitric oxide as a mediator of natriuretic peptide action was investigated by perfusion of n-nitro-L-arginine (10(-3) mol/L), an inhibitor of nitric oxide synthase. Attenuation of the action of atrial natriuretic peptide by placental peptidases was studied by perfusion with the peptidase inhibitor benzamidine (2 x 10(-2) mol/L). Statistical significance was determined by analysis of variance and paired t test.


RESULTS
Significant attenuation of vasoconstrictor responses to angiotensin II occurred within both atrial natriuretic peptide and brain natriuretic peptide; however, brain natriuretic peptide was more effective. n-Nitro-L-arginine did not affect the attenuation of angiotensin II-induced vasoconstriction by atrial or brain natriuretic peptides. In the presence of benzamidine atrial natriuretic peptide exerted a significantly greater vasodilator effect.


CONCLUSIONS
Brain natriuretic peptide is a more potent vasodilator of the placental vasculature than is atrial natriuretic peptide. The low efficacy of atrial natriuretic peptide may be related to placental peptidases. Nitric oxide does not mediate the action of atrial natriuretic peptide or brain natriuretic peptide.
Department of Obstetrics and Gynecology, University of Cincinnati College of Medicine, OH 45267-0526.
G
G
Holcberg
W
W
Kossenjans
A
A
Brewer
M
M
Miodovnik
L
L
Myatt
D000804:Angiotensin II / Q000494:pharmacology; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001550:Benzamidines / Q000494:pharmacology; D001808:Blood Vessels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D020097:Natriuretic Peptide, Brain; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D019335:Nitroarginine; D009994:Osmolar Concentration; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D014661:Vasoconstriction / Q000187:drug effects
D001550:Benzamidines; D009419:Nerve Tissue Proteins; D000804:Angiotensin II; D020097:Natriuretic Peptide, Brain; D019335:Nitroarginine; D009320:Atrial Natriuretic Factor; D001120:Arginine; C032157:benzamidine