Effect of intravenous L-alanine administration on plasma glucose, insulin and glucagon, blood pyruvate, lactate and beta-hydroxybutyrate concentrations in newborn infants. Study in term and preterm newborn infants.

Ten term and eleven preterm newborn infants with appropriate weights for their gestational age were infused for one minute with L-alanine (150 mg/kg) at the age of 29 to 76 hours (mean 48 hours) and circulating levels of glucose, lactate, pyruvate, D-betahydroxybutyrate (D-BOHB), insulin and glucagon were monitored. Plasma glucose concentrations increased from 2.7 +/- 0.16 (mean +/- S.E.M.) to 3.7 +/- 0.2 mmol/l after 50 min (p less than 0.01) in term infants. In preterm infants, after an initial decrease of the glucose level from 3.1 +/- 0.16 to 2.6 +/- 0.16 mmol/l (p less than 0.05), it returned to the baseline level at 50 min: 3.0 +/- 0.2 mmol/l. The blood concentration of D-BOHB decreased in term infants from 192 +/- 37 to 112 + 6 micrometer/l (p less than 0.01) after 40 min. In preterms, its decrease was not significant (p greater than 0.05). Plasma glucagon level rose from 53 +/- 5 to 70 +/- 8 pmol/l after ten minutes (p less than 0.01) in terms infants and from 61 +/- 6 to 75 +/- 9 after 20 min (p less than 0.01) in preterm infants. There were no significant changes in plasma insulin concentrations in either group. Forty minutes after L-alanine infusion, I/G ratios were lower in preterm infants (1.26 +/- 0.14) than in term infants (1.71 +/- 0.25) (p less than 0.01). There was no relationship between the glycemic responses to L-alanine and the basal levels of D-BOHB. The data suggest that the glycemic effect of L-alanine infusion and circulating glucagon depends upon a specific stage in maturation. The antiketogenic effect of L-alanine infusion is observed in term infants as in adults.