Acid-soluble nucleotides of human milk at different stages of lactation

The acid-soluble ribonucleotides of human milk were measured by enzymic and ion-exchange chromatographic procedures at different stages of lactation. Human colostrum and milk contained CMP, AMP, GMP, UMP, GDP-mannose, UDP-N-acetyl-glucosamine, UDP-N-acetyl-galactosamine, UDP-glucose, UDP-galactose, UDP and other minor nucleotides. Cytidine and adenosine derivatives were present in relatively higher amounts than in milk from ruminant species. The nucleotide concentration decreased with advancing lactation. Human milk at 3 months of lactation contained about 10 mumol/100 ml nucleotides, which represented about 75% of the amount of nucleotides present in human colostrum. Human milk did not contain orotic acid. The UDP-glucose/UDP-galactose ratio was constant during lactation and was similar to that of milks from ruminant species.