Picolinic acid in milk, pancreatic juice, and intestine: inadequate for role in zinc absorption.

Picolinic acid (PA) was measured by high pressure liquid chromatography in human milk and other fluids and tissues. Skimmed human milk, intestinal homogenates from human infants and rats, and human and rat pancreatic juice were ultrafiltered and analyzed by high pressure liquid chromatography using an anion-exchange column. Identity of sample components was verified by comparing retention times with those of pure nicotinic acid and PA. The detection limit for PA was 2.5 microM. Human milk contained less than 3.7 microM PA. PA was undetectable in human infant or rat intestine or in human or rat pancreatic juice. The extremely low concentration of PA in milk and its apparent absence in pancreatic juice and intestine provide additional evidence that PA is not the low molecular weight zinc binding ligand of human milk and that it does not have an important physiological role in intestinal zinc absorption.