Effect of suckling and diurnal influences on the concentrations of taurine and other free amino acids in milk.
Factors affecting the taurine and free amino acid content of human milk from a single donor have been examined. Taurine concentration was highest during the transition from colostrum to milk, attaining 400 microM. Concentrations fell thereafter, reaching 150 microM at 115 d post partum. Other free amino acids showed an opposite developmental pattern. Samples collected immediately after infant feeding were systematically lower in taurine than those collected immediately before feeding, but the differences were relatively small. Concentrations of other amino acids were unaffected by suckling on day 4. On day 6, however, decreases ranged from 16 per cent for glutamate to 46 per cent for threonine. Samples collected every 2 h over a 72-h period on days 113 to 115 post partum showed no diurnal variation in taurine content, neither did samples collected over a 24-h period on days 4, 6, 11, and 12. Serine and glycine showed a similar lack of periodicity. Aspartate, alanine, glutamine, threonine and glutamate levels, on the other hand, were lowest in the early morning, and highest in the early afternoon. High to low ratios ranged from 1.7 for glutamate to 4.1 for aspartate. Sample collection for taurine, serine and glycine analysis can probably be made without concern as to time of day or relationship to infant feeding. For the other amino acids, however, these factors need to be considered.
Shubat
P J
PJ
Department of Pharmacology, College of Medicine, University of Arizona, Tucson 85724.
Parker
D
D
Huxtable
R J
RJ
D000328:Adult; D000596:Amino Acids / Q000378:metabolism*; D001942:Breast Feeding; D002940:Circadian Rhythm; D003126:Colostrum / Q000378:metabolism; D005260:Female; D006801:Humans; D008895:Milk, Human / Q000378:metabolism*; D013391:Sucking Behavior; D013654:Taurine / Q000378:metabolism*
D000596:Amino Acids; D013654:Taurine