Effects of corticosteroids in preterm sheep on adaptation and sympathoadrenal mechanisms at birth.
This study investigates the effects of prenatal corticosteroid administration on newborn sympathoadrenal mechanisms involved in postnatal adaptation. Randomly assigned preterm (122-125 days) fetal sheep were treated with hydrocortisone or saline for 60 h and delivered by cesarean section. We examined postnatal physiological adaptation, sympathoadrenal responses, cardiac beta-receptor density, and the receptor-cyclase system. We observed increased ventilatory, cardiovascular, and metabolic responses function in the corticosteroid-treated animals despite a marked attenuation in the anticipated surge of plasma catecholamine concentrations and a decrease in epinephrine secretion rate, which is normally seen at birth. Myocardial beta-adrenergic receptor density and affinity states were comparable in both groups. Basal and agonist-mediated adenylyl cyclase activity in myocardial tissue was increased in the corticosteroid-treated animals. We speculate that the increase in myocardial adenylyl cyclase activity may be accompanied by similar changes in other organ systems and that this could account for the augmentation in respiratory, cardiovascular, and metabolic responses in the corticosteroid-treated animals.
Department of Pediatrics, Harbor-University of California, Los Angeles School of Medicine, Torrance 90502.
H M
HM
Stein
K
K
Oyama
A
A
Martinez
B A
BA
Chappell
E
E
Buhl
L
L
Blount
J F
JF
Padbury
D000064:Acclimatization / Q000187:drug effects; D000262:Adenylyl Cyclases / Q000378:metabolism; D000311:Adrenal Glands / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects*; D001835:Body Weight; D002302:Cardiac Output / Q000187:drug effects*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004837:Epinephrine / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000502:physiology; D005865:Gestational Age; D006854:Hydrocortisone / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D009638:Norepinephrine / Q000097:blood*; D009929:Organ Size; D011247:Pregnancy; D012016:Reference Values; D012044:Regression Analysis; D012119:Respiration / Q000187:drug effects; D012756:Sheep; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D005576:Colforsin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D006854:Hydrocortisone; D009638:Norepinephrine; D004837:Epinephrine