Peripheral plasma concentrations of somatostatin-like immunoreactivity in newborns and infants.

Postprandial peripheral plasma concentrations of somatostatin-like immunoreactivity (SLI) were measured by RIA after extraction with acetone-petroleum ether in 98 normal newborns and infants. In 62 subjects, plasma concentrations of gastrin were determined simultaneously. The plasma levels of SLI increased progressively with age during the neonatal period. The mean plasma levels of SLI increased significantly from 19.5 +/- 7.5 (+/- SD) pg/ml in 29 cord blood samples to 29.0 +/- 17.2 pg/ml in 36 newborns aged 1-5 days. The mean postprandial level of plasma SLI was significantly higher in 18 infants aged 1-3 months (45.5 +/- 25.8 pg/ml) than in newborns and tended to decrease in infants aged 7-10 months after weaning (31.6 +/- 7.9 pg/ml). The mean postprandial levels of plasma SLI were significantly higher in newborns and infants less than 10 months old than in older children aged 8-12 yr (10.2 +/- 3.7 pg/ml). The gel filtration patterns of SLI of plasma extracts were similar in infants and older children. The changing pattern of mean plasma gastrin with age was similar to that of SLI, and individual plasma levels of SLI were significantly correlated with those of gastrin during the neonatal period. High concentrations of SLI are present in the peripheral circulation during the first 10 months of life. Thus, this peptide may play a significant role as a hormone in nutrient homeostasis in infants.