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Eight proteins (Immunoglobulin A, G, M, C3 and C4 fractions of complement, alpha 1-glycoprotein, lactoferrin and alpha 1- antitrypsin) were measured by immuno-diffusion or laser nephelometry in 50 milk samples. Thirty nine were heated thrice at 62 degrees C for 20 minutes. Twenty six came from mothers who delivered prematurely (less than 37 weeks) and 13 from mothers who delivered at term. Eleven samples were, used to determine the effect of the heating process. There was no significative difference of the concentrations of the eight proteins between the breast milk obtained at term or prematurely, even when the comparisons were made between colostral milks or transitional milks. The heating process reduced the concentration by 47 % for IgA, more than 88 % for IgG and IgM, 41 to 74 % for the other proteins; only orosomucoid seemed little affected (-16 %). These data suggest that the heating process impairs the immunologic effect of breast milk. This effect must be particularly considered in regard to the absence of any significant difference between the milks obtained at term or prematurely.

The authors describe the optimization of determination of alanine aminopeptidase (AAP), gamma-glutamyltransferase (GGT) and N-acetyl-beta-D-glucosaminidase (NAG) in urine by multivariate analysis. The optimal conditions found are: for AAP at 30 degrees C TRIS HCl buffer 300 mmol/l pH 7.9, L-alanine-4-nitroanilide 5.8 mmol/l, for GGT at 30 degrees C buffer glycylglycine 150 mmol/l pH 8.0, gamma-L-glutamyl-3-carboxy-4-nitroanilide 9.0 mmol/l, for NAG at 37 degrees C citrate buffer 50 mmol/l pH 5.8, m cresolsulfonphtaleinyl-N-acetyl-beta-D-glucosaminide 5.5 mmol/l. These methods are easy to perform, apply to urine without pretreatment through Sephadex: therefore complete automatization is possible. The stability of enzymatic activities in urine is of ten days at +4 degrees C in the presence of sodium azide at neutral pH. Freezing resulted in a considerable loss of activity for AAP and GGT.