Table 1.
In vivo studies in sheep and in vitro studies of isolated human placental and umbilical blood vessels demonstrate the umbilical-placental circulation is responsive to a variety of vasoactive substances. However, it should be noted that some vasodilators (*) exert their effects in vitro only when vessels are pre-constricted with another substance. Compiled from several sources [90–100].
| Substance | Umbilical artery and placental resistance (sheep) | Isolated placental or umbilical artery or vein (human) |
|---|---|---|
| Acetylcholine | constrict | |
| Adenosine | ↔ | |
| Angiotensin II | ↑ | constrict |
| Bradykinin | constrict | |
| Endothelin 1 | ↑ | |
| Epinephrine | ↑ | constrict |
| Forskolin | ↓ | dilate |
| Histamine | constrict | |
| Isoproteranol | ↔ | |
| Neurokinin B* | dilate | |
| Nitrogycerin* | ↔ | dilate |
| Norepinephrine | ↔ | constrict |
| Oxytocin | constrict | |
| Potassium | constrict | |
| Prostacyclin* | ↔ | dilate |
| Prostaglandin A1 | constrict | |
| Prostaglandin F2α | constrict | |
| Prostaglandin I2 | ↔ | |
| Serotonin | constrict | |
| U-46619 (thromboxane mimetic) | constrict | |
| Vasopressin | ↑ | constrict |