Alpha-1-antitrypsin and IgA in serial meconium and faeces of healthy breast-fed newborns.

Background: Meconium is a series of layers formed in the foetal intestine from the 12th week of gestation. High content of meconial alpha-1-antitrypsin (AAT), decreasing within the first several days of extrauterine life appears to reflect the meconium clearance of the gut. At birth, IgA is not present in the meconium and breast-fed infants receive this antibody postnatally with human milk. The aim of the study was to determine changes in AAT concentrations, functional activity of that inhibitor expressed as trypsin inhibitory capacity (TIC) and IgA concentration in serial meconium and faeces, as endogenous biochemical markers discriminating between faeces portions formed in intrauterine and extrauterine life periods of healthy breast-fed newborns.

Methods: A group of 24 healthy breast-fed newborns delivered by spontaneous labour were studied prospectively during the first 4 days of postnatal life. AAT and IgA concentrations in the newborn's meconial and faecal samples and IgA concentration in mother's milk samples taken on the third day after delivery, were determined by radial immunodiffusion. TIC was assessed using BAPNA (N-benzoyl-DL-arginine-p-nitroanilide).

Results: The medians (range) of AAT concentrations in milligrams per gram of dry meconium or faeces were: 68.8(29.2-138.4) (day 1), 56.9 (30.8-112.8) (day 2), 26.2 (6.8-80.7) (day 3), and 6.6 (1.4-27.1) (day 4). The medians (range) of TIC in milligrams of trypsin/g dry mass of meconium or faeces were: 0.76 (0.33-1.79) (day 1), 0.44 (0.17-1.08) (day 2), 0.16 (0.03-0.56) (day 3), and 0.03 (0-0.11) (day 4). The median (range) of IgA concentration in mothers' milk was 715 mg/dl (420-890). IgA was absent in meconium portions from the first day of life while on the successive days the medians (range) of IgA concentration in mg/g dry mass of meconium and faeces were as follows: 0 (0-2.90) (day 2), 2.50 (1.10-9.60) (day 3), 7.05 (4.10-30.60) (day 4). On day 4 of extrauterine life a negative correlation was found between AAT and IgA concentrations in faeces of the newborns (r = -0.46) and a positive correlation was seen between IgA concentrations in faeces and milk (r = 0.93).

Conclusions: Analyses of the systematic decrease in AAT and increase of IgA concentration in serial portions of meconium and faeces over the first days of extrauterine life of breast-fed newborns can date newborn's faeces portions formed during intrauterine and extrauterine maturation. AAT deposited in foetal intestine is an active antiprotease.