URINARY ENDOTHELIN EXCRETION IN THE NEONATE - INFLUENCE OF MATURITY AND PERINATAL PATHOLOGY

The present study was undertaken to establish the developmental patter n of urinary endothelin-1 (ET-1) excretion and to define its possible role in mediating pathophysiological changes related to perinatal asph yxia/infection and dopamine treatment. Urinary ET-1 levels were measur ed by radioimmunoassay in 7 full-term neonates (mean gestational age 3 9.3 weeks) on days 1, 3 and 5, and in 9 pre-term neonates (mean gestat ional age 30.8 weeks) on days 1, 3, 5, 7 and weekly thereafter for 5 c onsecutive weeks. The results were compared with those of three age-gr oups of 30 normal children (4-8 years, 9-12 years and 13-18 years); ea ch group consisted of 10 children. The influence of severe cardiopulmo nary distress (n = 16, mean gestational age 33.9 weeks, post-natal age 3.3 days) and dopamine administration in a dose of 2 mu g/min per kg (n = 10, mean gestational and post-natal ages 32.1 weeks and 5.6 days, respectively) were also studied. In full-term infants, ET-1 concentra tion fell from 34.3 +/- 1.8 pmol/l on day 1 to 21.5 +/- 1.5 pmol/l on day 5 (P <0.01). In premature infants its absolute value and its post- natal fall were similar in the 1st week and no further change occurred in weeks 2-5; it stabilized at levels between 17.1 +/- 2.2 and 16.7 /- 1.7 pmol/l. These concentrations tended to be lower than those of 2 5.5 +/- 1.3, 23.0 +/- 1.0 and 26.2 +/- 0.7 pmol/l measured in three gr oups of older children. During the 1st week, daily ET-1 excretion rema ined unchanged in term infants (3.1 +/- 1.0 vs. 3.7 +/- 1.5 pmol/m(2) per day), but there was a significant increase from 6.5 +/- 1.0 to 12. 4 +/- 0.7 pmol/m(2) per day (P <0.01) in premature infants. During wee ks 2-5, preterm infants excreted more ET-1 than older children (P <0.0 1). In response to perinatal ashphyxia/infection and dopamine therapy, urinary ET-1 excretion markedly rose and there was a significant posi tive correlation between urine flow rate and ET-1 excretion (P <0.001) . We conclude that ET-1 concentration rather than excretion rate may h ave a role in mediating the changes in renal functions that occur soon after birth. The pathophysiological significance of the now-dependent increase in urinary ET-1 excretion needs to be further studied.