INAPPROPRIATE SECRETION OF UMBILICAL PLASMA-CATECHOLAMINES IN PRETERMCOMPARED TO TERM NEONATES

To investigate the gestation and stimulus related catecholamine secret ion and degradation at birth free and sulfoconjugated adrenaline, nora drenaline and dopamine were analysed in the umbilical artery and vein of 35 preterm and 75 term neonates. A highly sensitive radioenzymatic assay was used for the determination of free catecholamine levels, sul foconjugated catecholamines were analysed after addition of 25 mU aryl sulfatase type VI. Levels of free catecholamines were significantly lo wer in preterm as compared to term newborns. Hereby, adrenaline levels significantly correlated with the gestational age, birth weight, and birth length. Sulfoconjugated catecholamine levels were similarly lowe r, but only sulfoconjugated noradrenaline reached differences of stati stical significance. The placental extraction rate of adrenaline and n oradrenaline was significantly lower in preterm as compared to term ne onates. Only in term but not in preterm neonates, arterial pH- and pCO (2)-levels significantly correlated with arterial plasma catecholamine levels. Therefore, lower catecholamine levels in preterm compared to term neonates result from lower secretion of catecholamines rather tha n increased degradation and may contribute to their frequent surfactan t deficiency. In addition, the inadequate and diminished catecholamine secretion of preterm neonates may play a significant part in their po stnatal adaptation problems like hypoglycaemia, hypothermia and occurr ence of wet lungs.