Abstract
Arginine vasotocin (AVT) is found in the mammalian fetal pineal and was previously shown to decrease water flow across guinea pig placental membranes in vitro. To examine this effect in vivo we infused mannitol (Osmitrol 500 ml in a 20% solution) into 6 chronically catheterized ewes (129-144 days gestation). Fetal and maternal blood gases, pH, blood pressure (BP), heart rate (HR), hematocrit (Hct), and osmolality (Osm) were measured at eight 10 minute intervals before and after the mannitol. One day later an identical amount of mannitol was infused into the ewe during a 2hr infusion of AVT into the fetal circulation,with similar blood sampling. In 4 control ewes 500 ml normal saline (NS) was infused in place of the mannitol.
Maternal mannitol infused without fetal AVT evoked a greater rise in mean (±SEM) fetal osm (baseline 291 ± 2.1 mOsm/kg vs post mannitol 313 ± 6.1 mOsm/kg) than did maternal mannitol during fetal AVT infusion (289 ± 1 vs 297 ± 3.1 mOsm/kg; p<.05).During the AVT infusion fetal HR, pH and pO2 remained unchanged; fetal pCO2 increased from 30 ± 2 to 37 ± 4 (p<.05). Fetal BP increased from 64 ± 3 to 75 ± 2 mmHg (p<0.01). NS infusion produced no change in any parameter.
Thus: 1)AVT in the fetal circulation diminishes water transfer from fetus to mother in response to a maternal osmolar stimulus; 2)This effect may be mediated by decreased fetal/placental blood flow or by a direct AVT effect on placental water transfer.
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Leake, R., Palmer, S., Oakes, G. et al. 262 ARGININE VASOTOCIN INHIBITS OVINE FETAL/MATERNAL WATER TRANSFER. Pediatr Res 15 (Suppl 4), 483 (1981). https://doi.org/10.1203/00006450-198104001-00273
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DOI: https://doi.org/10.1203/00006450-198104001-00273