Hm. Stein et al., EFFECTS OF CORTICOSTEROIDS IN PRETERM SHEEP ON ADAPTATION AND SYMPATHOADRENAL MECHANISMS AT BIRTH, The American journal of physiology, 264(5), 1993, pp. 763-769
This study investigates the effects of prenatal corticosteroid adminis
tration on newborn sympathoadrenal mechanisms involved in postnatal ad
aptation. Randomly assigned preterm (122-125 days) fetal sheep were tr
eated with hydrocortisone or saline for 60 h and delivered by cesarean
section. We examined postnatal physiological adaptation, sympathoadre
nal responses, cardiac beta-receptor density, and the receptor-cyclase
system. We observed increased ventilatory, cardiovascular, and metabo
lic responses function in the corticosteroid-treated animals despite a
marked attenuation in the anticipated surge of plasma catecholamine c
oncentrations and a decrease in epinephrine secretion rate, which is n
ormally seen at birth. Myocardial beta-adrenergic receptor density and
affinity states were comparable in both groups. Basal and agonist-med
iated 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 cha
nges in other organ systems and that this could account for the augmen
tation in respiratory, cardiovascular, and metabolic responses in the
corticosteroid-treated animals.