Somatostatin in preterm infants: postnatal changes and response to stress

To determine the chronology of postnatal somatostatin (SRIF) changes in preterm infants and the relationship of SRIF levels to respiratory and gastrointestinal complications, we evaluated sequential SRIF levels in 62 preterm infants in the first month of life. Weekly preprandial plasma samples were obtained and analyzed for SRIF using a radioimmunoassay. Additional blood samples were obtained at the time of abdominal events. Somatostatin levels were highest in week 2 and gradually declined in weeks 3 and 4 (mean +/- SD pmol/l, SRIF = 92.3 +/- 30.3 in week 2 vs. 79.8 +/- 33.9 in week 3 and 69.7 +/- 54.4 in week 4, p < 0.03). Birth weight, gestational age and sex were not related to initial SRIF levels. Infants with respiratory distress requiring assisted ventilation had significantly higher week 1 SRIF levels compared to infants without respiratory problems (97.9 +/- 22.7 vs. 74.9 +/- 21 pmol/l, p < 0.02). Twenty-one of the 62 infants had gastrointestinal complications. Somatostatin levels preceding (89.0 +/- 25.9 pmol/ 1), during (91.0 +/- 13.3) and after (79.3 +/- 28.6) the gastrointestinal events were not significantly different, nor were they different from SRIF concentrations of age-matched preterm infants without gastrointestinal complications. The results suggest that in preterm infants, postnatal SRIF changes follow a definite pattern with peak concentrations in week 2. Respiratory distress is associated with a significant increase in SRIF. However, subsequent gastrointestinal events do not lead to an increase in SRIF. This lack of SRIF response in gastrointestinal stress may play a role in the pathogenesis of gut injury in the premature neonate.