Vasoconstrictive activity of oxytocin in meconium impregnated human placentas.
OBJECTIVE
The aim of our study is to determine whether oxytocin acts differently on the fetal-placental vascular bed of normal and meconium impregnated placentas.


METHODS
Isolated placental cotyledons (n=10) were dually perfused with fetal perfusion pressure used as an index of vascular resistance. As perfusion medium we used lactated Ringer salt solution, containing polyvinylpyrolidone (25 g/l), bovine serum albumin (0.1 mg/ml), glucose (1.0 g/l), heparin (20 IU/ml) and gentamycin (48 microg/ml). The pH of the medium was adjusted to 7.4 with bicarbonate. The maternal site was gassed with 95% O(2):5% CO(2) and in the fetal site with 95% N(2):5% CO(2) at 37 degree C. Perfusion rates were 4-6 and 10-12 ml/min in the fetal and maternal circulation, respectively. TNF-alpha and IL-beta1 levels in the fetal-placental perfusate were evaluated using specific commercial ELISA kits.


RESULTS
No significant changes in the amount of TNF-alpha release were observed after injection of oxytocin into the fetal circulation (31+3pg/ml; P=0.5). No IL-beta1 activity was observed in the fetal perfusate of normal and meconium impregnated placentas during the experiments. No significant difference was seen in basal perfusion pressure in normal and meconium impregnated placentas, however, a bolus injection of oxytocin (10U/ml) resulted in a significant increase in perfusion pressure in meconium impregnated placentas from basal pressure of s45+5 to 88+4 mm Hg after injection of oxytocin, (P=0.004, ANOVA).


CONCLUSIONS
Vasoconstrictive effect of oxytocin was observed only in meconium impregnated placentas and no vascular effect of oxytocin was documented in normal placentas. The clinical implication of our findings is that one should use oxytocin for stimulation of labor with caution in the presence of meconium stained amniotic fluid.
Holcberg
Gershon
G
Department of Obstetrics and Gynecology, Faculty of Health Sciences, Soroka University Medical Center, Ben Gurion University of The Negev, P.O. Box 151, 84101 Beer Sheva, Israel. holcberg@bgumail.bgu.ac.il
Sapir
Olga
O
Huleihel
Mahmoud
M
Triger
Mark
M
Lazer
Simcha
S
Katz
Miriam
M
Mazor
Moshe
M
Schneider
Henning
H
D016022:Case-Control Studies; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000378:metabolism; D008470:Meconium; D010121:Oxytocin / Q000494:pharmacology*; D010477:Perfusion; D010920:Placenta / Q000187:drug effects* / Q000378:metabolism; D011247:Pregnancy; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D014662:Vasoconstrictor Agents; D010121:Oxytocin