Human alpha-lactalbumin and bovine beta-lactoglobulin absorption in premature infants.

The absorption of a-lactalbumin (ALA) and proteolysis, and motility of the intestine. Until the 40th wk of bovine @-lactoglobulin (BLG) was investigated in 23 gestation, these factors are not fully developed, which can be healthy preterm infants with gestational ages of 32 to 36 seen by the greater penetration of isologous protein through the wk. The concentrations of ALA and BLG in serum after a intestinal epithelium in preterm rather than in full-term infants milk feeding were measured at intervals during the first 8 (7, 8). The absorption of heterologous proteins is dependent on mo of life. We used a time-resolved fluoroimmunoassay to local and systemic immune responses (9, 10). measure the proteins. Measurable amounts of ALA were The aim of the present study was to follow up the permeability found on d 7 after birth, and at 1, 2, 3, 5, and 8 mo in 23 of the gut in premature infants and to compare it with that of of 23, 13 of 18, 13 of 18, six of 17, eight of 16, and five of full-term infants studied earlier (1 1). To gain a better picture of 13, respectively, of the infants tested; median serum levels the permeability, we used two different proteins: ALA, which of ALA at the respective ages were 120 (range,.19-2598), elicits no immune response, and BLG, a major antigen in CM. 16 (range, 0-177), 5 (range, 0-40), 0 (range 0-3), 0.8 (range 0-38), and 0 (range, 0-22) pg/L serum/g ALA given/ kg body wt, respectively. The rate of decline in ALA MATERIALS AND METHODS absorption was comparable among the infants. Tests for Slrbjects andsanlpling. With the informed and written consent BLG were begun after the introduction of cow's milk. At of the mothers, 23 healthy premature infants with a median 2,3,5, and 8 mo of age BLG was detected in two of 7, two gestational age of 34 wk (range, 32.6-36.6) were recruited into of 9, eight of 10, and two of 12, respectively, of the infants the study on d 3-4. All infants were healthy and free of perinatal tested, where median levels in positive cases were 13, 17, infections, and enteral feeding was started on the 1st postnatal 15, and 3 pg/L serum/g BLG givenlkg, respectively. The d. Two infants received supplemental i.v. infusions, and four amounts of absorbed ALA and BLG were lo-' to of infants received part of the feeding as nasogastric boluses via a the oral dose. Serum levels of ALA or BLG did not depend tube during the 1st days of life. Four infants dropped out after on the gestational age of the infant. Few of the infants had the initial visit because of difficulties in traveling to the hospital. any detectable absorption of either protein shortly after The infants were examined postnatally and at the ages of 1, 2, 3, weaning. Thus, systemic absorption of ALA and BLG does 5, and 8 mo. They were also seen immediately before the planned occur in preterm infants. Absorption of ALA is significant weaning and 1 and 2 wk after it. Before weaning, the mothers for a few months after birth but then decreases rapidly. were advised to use a CM-free diet. Feeding recommendations (Pediatr Res 35: 344-347,1994) included fruit, berries, and vegetables from 3 mo and meat, fish, eggs, and cereals from 5 mo. Infants attended well-baby clinics,