HUMAN ALPHA-LACTALBUMIN AND BOVINE ALPHA-LACTOGLOBULIN ABSORPTION IN PREMATURE-INFANTS

The absorption of cr-lactalbumin (ALA) and bovine beta-lactoglobulin ( BLG) was investigated in 23 healthy preterm infants with gestational a ges of 32 to 36 wk. The concentrations of ALA and BLG in serum after a milk feeding were measured at intervals during the first 8 mo of life . We used a time-resolved fluoroimmunoassay to measure the proteins. M easurable amounts of ALA were found on d 7 after birth, and at 1, 2, 3 , 5, and 8 mo in 23 of 23, 13 of 18, 13 of 18, six of 17, eight of 16, and five of 13, respectively, of the infants tested; median serum lev els of ALA at the respective ages were 120 (range, 19-2598), 16 (range , 0-177), 5 (range, 0-40), 0 (range 0-3), 0.8 (range 0-38), and 0 (ran ge, 0-22) mu g/L serum/g ALA given/ kg body wt, respectively. The rate of decline in ALA absorption was comparable among the infants. Tests for BLG were begun after the introduction of cow's milk. At 2, 3, 5, a nd 8 mo of age BLG was detected in two of 7, two of 9, eight of 10, an d two of 12, respectively, of the infants tested, where median levels in positive cases were 13, 17, 15, and 3 mu g/L serum/g BLG given/kg, respectively. The amounts of absorbed ALA and BLG were 10(-5) to 10(-3 ) of the oral dose. Serum levels of ALA or BLG did not depend on the g estational age of the infant. Few of the infants had any detectable ab sorption of either protein shortly after weaning. Thus, systemic absor ption of ALA and BLG does occur in preterm infants. Absorption of ALA is significant for a few months after birth but then decreases rapidly .