Proteins in preterm and term milk from mothers delivering appropriate or small-for-gestational age infants

Abstract

The concentrations of total protein, secretory immunoglobulin A (IgA), lactotransferrin (LTF) and serum albumin (SA) were measured in sequential samples of colostrum, transitional and mature milk from 53 mothers divided into four groups according to gestational age and birthweight of their infants. Individual proteins were determined by single radial immunodiffusion. From the covariance analysis of data controlling for the day of lactation and the milk volume it was found that these covariables were significantly negative correlated with total protein and IgA. The concentration of LTF was also significantly negative correlated with the day but positively with the volume; whereas the contrary occurs for SA although the correlation was not significant for the volume. Differences in the total protein and IgA contents have been found among the mothers. The LTF content varied among the groups. Mean protein contents did not change in a similar way in all groups during lactation. Preterm milk maintained a more constant level of proteins.