Rebound increase in fetal breathing movements after 24-h prostaglandin E2 infusion in fetal sheep.
We investigated the hypothesis that the precipitous decrease in prostaglandin E2 (PGE2), a potent inhibitor of fetal breathing, from high plasma concentrations during labor causes a rebound stimulation of breathing without newborn concentrations falling below prelabor fetal values. Fetal plasma PGE2 concentration was gradually increased from 384 +/- 82 (SE) pg/ml in 2-h steps [0 (baseline), 1.5, 3, and 6 micrograms/min] to labor levels (1,230 +/- 381 pg/ml at 6 micrograms/min) and then was maintained for 24 h (n = 9). PGE2 at 1.5 micrograms/min significantly decreased breathing incidence [from 42 +/- 4 (baseline) to 14 +/- 4%] and breath amplitude (from 2.1 +/- 0.5 to 1.5 +/- 0.2 arbitrary units) and increased breath-to-breath interval (from 1.16 +/- 0.07 to 1.56 +/- 0.06 s). No further dose-related changes were observed. During the first 2 h after PGE2 infusion was stopped, PGE2 concentration returned to basal (352 +/- 64 pg/ml) but breathing incidence and amplitude were significantly higher (74 +/- 8% and 2.4 +/- 0.3 arbitrary units, respectively) and breath-to-breath interval was significantly lower (0.95 +/- 0.10 s) than were basal levels. Changes arose within approximately 15 min and were maintained for at least 4 h. Breathing did not change significantly in the saline-treated group (n = 7). Results suggest that the rapid decrease in plasma PGE2 concentration at birth promotes the onset of breathing.
Hollingworth
S A
SA
Program in Development and Fetal Health, Mount Sinai Hospital, Toronto, Canada.
Jones
S A
SA
Adamson
S L
SL
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology; D015232:Dinoprostone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004576:Electromyography; D004967:Estrogens / Q000097:blood; D005260:Female; D005324:Fetal Movement / Q000187:drug effects*; D006340:Heart Rate, Fetal / Q000502:physiology; D009638:Norepinephrine / Q000097:blood; D010120:Oxytocics / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D011863:Radioimmunoassay; D015656:Respiratory Mechanics / Q000187:drug effects*; D012756:Sheep
D004967:Estrogens; D010120:Oxytocics; D011374:Progesterone; D000324:Adrenocorticotropic Hormone; D015232:Dinoprostone; D009638:Norepinephrine