Abstract
During premature parturition induced by ACTH there is a rise in fetal AVP only after the onset of labor. Fetal AVP levels which peak at delivery are not related to maternal levels which rise only during pushing. To investigate the characteristics of AVP release as measured by radioimmunoassay, 9 fetal lambs were instrumented at 121 days gestation. At 129 days, 7 fetuses were infused at 1.5 ml/hr with ACTH (10 mg/kg/hr) and 2 with saline. Delivery occurred after a mean of 74 hours of ACTH infusion.
During infusion fetal pH (7.36 ± .002 S.E.) and pCO2 (42 ± 2 mmHg) remained constant while PO2 decreased (22 ± 2 to 18 ± 2 mmHg, r = .96). Serum electrolytes and osmolarity remained stable through infusion and early labor (Cl 109.5 ± 1.5 meq/L, Na 145 ± 1.3 meq/L, K 4.0 ± .45 meq/L and osmolarity 289 ± 3.2 mOsm/L). Fetal AVP rose from prelabor mean values of 1.8 ± 1.8 pg/ml to 40 ± 73 pg/ml in active labor, 173±404 pg/ml in the pushing phase and 720±1470 pg/ml at delivery, then decreased 30 minutes after delivery to 360 ± 340 pg/ml. During labor serial fetal arterial AVP levels were compatible with pulsatile release unrelated to uterine contractions. In ACTH induced parturition the AVP rise is not related to the initiation of labor or changes in serum osmolarity but may be related to changes in fetal oxygenation. We speculate that the high levels of AVP may be instrumental in fetal cardiovascular adjustments to the stress of labor.
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Stork, R., Hussoin, K., Doniel, S. et al. CHARACTERISTICS OF VASOPRESSIN (AVP) RELEASE DURING ADRENOCORTICOTROPHIN (ACTH) INDUCED PARTURITION IN THE LAMB. Pediatr Res 11, 412 (1977). https://doi.org/10.1203/00006450-197704000-00257
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DOI: https://doi.org/10.1203/00006450-197704000-00257