Abstract
Simultaneous maternal and fetal plasma oxytocin (OXY) concn. (μU/ml) were measured by radioimmunoassay before and during continuous infusion of synthetic OXY to steady state conditions into ewe or fetus (gestational age 124-140 days; at least 5 days post-surgery; estimated fetal wt. 3 kg).
Fetal metabolic clearance rates (MCR in ml/kg/min) were calculated to be 18.1 ± 1.1 and 15.0 ± 1.3 at the two infusion rates; maternal MCR were 12.7 ± 2.8 and 13.4 ± 2.3, respectively. Examination of simultaneous fetal and maternal baseline OXY concentrations revealed that fetal levels were significantly higher than maternal: 1.9 ± 0.2 vs 0.7 ± 0.1 (p<.05). Continuous monitoring of uterine pressure revealed that uterine contractions were induced by maternal infusion of 800 μU/kg/min; no uterine contractions were induced by fetal infusion. Conclusions based on these data are: 1) plasma OXY levels exceed maternal levels in fetuses of 124-140 days gestation; 2) transplacental passage of OXY is minimal in both M-F and F-M directions; 3) maternal and fetal MCR of OXY are similar and unrelated to plasma OXY levels.
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Glatz, T., Weitzman, R., Nathanielsz, P. et al. 298 METABOLIC CLEARANCE RATE OF OXYTOCIN IN MATERNAL AND FETAL SHEEP. Pediatr Res 12 (Suppl 4), 413 (1978). https://doi.org/10.1203/00006450-197804001-00303
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DOI: https://doi.org/10.1203/00006450-197804001-00303