Details

Autor(en) / Beteiligte

• Myatt, Leslie
• Brewer, Anthony S.
• Langdon, Gretchen
• Brockman, Diane E.

Titel

Attenuation of the vasoconstrictor effects of thromboxane and endothelin by nitric oxide in the human fetal-placental circulation

Ist Teil von

• American journal of obstetrics and gynecology, 1992, Vol.166 (1), p.224-230

Ort / Verlag

Philadelphia, PA: Mosby, Inc

Erscheinungsjahr

1992

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• Objective: We hypothesized that the endothelial-derived relaxing factor nitric oxide may contribute to low resting vascular tone and may attenuate vasoconstrictor action in the human fetal-placental circulation. Study design: Isolated human placental cotyledons were dually perfused in vitro, and the effects of N-monomethyl- L-arginine and N-nitro- L-arginine (3 × 10 −4 mol/L), which are nonmetabolizable analogs of L-arginine, the substrate for nitric oxide synthase, on resting perfusion pressure and on the fetal-placental circulation preconstricted with U46619 (10 −8 mol/L) or endothelin-1 (10 −8 mol/L) were established. Responses before and after inhibition were compared by paired f test. The effects of glyceryl trinitrate (10 −6 mol/L), acetylcholine (10 −4 mol/L), the calcium ionophore A23187 (10 −6 mol/L), and histamine (10 −8 to 10 −4 mol/L) were also determined in the preconstricted fetal-placental circulation. Results: Both N-monomethyl- L-arginine and N-nitro- L-arginine (3 × 10 −4 mol/L) increased resting perfusion pressure ( p < 0.06), and N-nitro- L-arginine promptly and significantly increased perfusion pressure in the fetal-placental circulation preconstricted with U46619 ( p < 0.0004) or endothelin-1 ( p < 0.06). Nitric oxide generated by addition of glyceryl trinitrate (10-6 mol/L) attenuated the vasoconstrictor effects of U46619 ( p < 0.026) or endothelin-1 ( p < 0.01). Neither acetylcholine nor the calcium ionophore A23187 had an effect on the fetal-placental circulation, whereas bradykinin further increased perfusion pressure. Histamine only relaxed the preconstricted preparations at concentrations (10 −6 to 10 −4 mol/L) above those shown to release nitric oxide in other systems. Conclusion: The stimulus to nitric oxide generation in the fetal-placental circulation may be hydrodynamic. Nitric oxide appears to contribute to maintenance of basal vascular tone and to attenuate the actions of vasoconstrictors in this circulation.