ANTENATAL DEXAMETHASONE TREATMENT DECREASES PLASMA-CATECHOLAMINE LEVELS IN PRETERM INFANTS

Antenatal corticosteroid therapy (ACT) has many beneficial effects on preterm infants. The cellular mechanisms of action of ACT include beta -adrenergic receptor-mediated cAMP generation. This study investigated the effects of ACT on sympathoadrenal mechanisms during immediate pos tnatal adaptation of preterm infants. Plasma epinephrine, norepinephri ne, 3,4-dihydroxyphenylglycol, and cAMP were measured within 12 h afte r birth in 103 preterm infants (gestational age 24-36 wk), who were di vided into two groups (non-ACT and ACT group) according to whether the mother had received dexamethasone treatment. Infants in the ACT group had significantly lower concentrations of plasma catecholamines than infants in the non-ACT group; plasma epinephrine was 38% lower, and pl asma norepinephrine was 20-40% lower in the ACT group, depending on ge stational age (r = -0.37 in the nan-ACT group and r = -0.28 in the ACT group, p < 0.05. Plasma cAMP concentrations were similar in the two g roups. Antihypertensive treatment of the mother was associated with lo w plasma cAMP (p < 0.001), whereas tocolytic treatment was associated with high plasma cAMP (p = 0.001) of the infant. The results indicate that ACT attenuates the birth-related increase in plasma catecholamine s. Still, plasma cAMP levels remain high, which suggests enhanced beta -adrenoceptor signaling after ACT.