Preterm lung function after retreatment with antenatal betamethasone in preterm lambs.
OBJECTIVE
We hypothesized that two doses of betamethasone administered 1 week apart would further enhance postnatal pulmonary function in preterm lambs (compared with a single dose).


METHODS
Fetal sheep (121 days' gestation) randomly received saline solution or betamethasone (0.5 mg/kg) as a single injection. Six days later fetal sheep were retreated with either saline solution or corticosteroid, and postnatal lung function was evaluated 1 day later.


RESULTS
Betamethasone improved compliance and ventilation efficiency index nearly 50%, and total lung volume increased twofold. No effects of treatment-to-delivery interval (1 vs 7 days) or corticosteroid retreatment on pulmonary function were apparent. Although surfactant pool sizes increased as a function of duration of exposure, no additional effect of corticosteroid retreatment was noted. Antenatal betamethasone increased messenger ribonucleic acid levels for the surfactant proteins A and C, and retreatment augmented surfactant protein B messenger ribonucleic acid levels but suppressed surfactant protein A and C messenger ribonucleic acid.


CONCLUSIONS
Improved postnatal lung function resulting from antenatal betamethasone was not augmented by retreatment.
Polk
D H
DH
Perinatal Research Laboratories, Harbor-University of California, Los Angeles, Medical Center, Torrance 90502, USA.
Ikegami
M
M
Jobe
A H
AH
Sly
P
P
Kohan
R
R
Newnham
J
J
D000818:Animals; D000831:Animals, Newborn; D001623:Betamethasone / Q000494:pharmacology*; D004334:Drug Administration Schedule; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism; D008170:Lung Compliance / Q000187:drug effects; D008297:Male; D010713:Phosphatidylcholines / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012123:Pulmonary Ventilation / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012756:Sheep
D005938:Glucocorticoids; D010713:Phosphatidylcholines; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; D001623:Betamethasone