Fields of application and results of analytic procedures with 15N in pediatric alimentary research

Investigation of protein metabolism in nutritional pediatric research by means of 15N tracer techniques has been relatively seldom used up to now. 15N labelled compounds for these purposes are not injurious to health. The technique is based on oral or intravenous application of the tracer substances and on 15N analysis of the urine fractions. The subsequent calculation of protein synthesis and breakdown rate, turnover and reutilisation of amino acids from protein breakdown as well as the size of the metabolic pool offers detailed information of protein metabolism. Determination of these parameters was performed in infants on mother's milk and formula feeding and on chemically defined diet. As an example of utilisation of D-amino acids for protein synthesis the 15N-D-phenylalanin retention on parenteral nutrition was found to be 33% of the applied dosis at an average. An oral 15N glycine loading test proved to be of value for the prediction of the therapeutic effect of human growth hormon in numerous types of dwarfism. Further application of 15N tracer technique dealt with utilisation of 15N urea for bacterial protein synthesis of the intestinal flora and with incorporation of 15N from 15N glycine and 15N lysine into the jejunal mucosa for measuring the enterocyte regeneration. (author)