Histamine as a ligand in blood plasma. Part 5. Computer simulated distribution of metal histamine complexes in normal blood plasma and discussion of the implications of a possible role of zinc and copper in histamine catabolism.

Previously physiological experiments carried out on mice have proved that copper and zinc can interfere with the pharmacological effects of histamine that lead to anaphylactic shock. A quantitative study of the interactions between essential metal ions and histamine in plasma was thus undertaken. The progressive approach towards a reliable computer-simulated distribution of the histamine-containing plasma species necessitated a large series of physicochemical determinations of the formation constants of the binary and ternary metal complexes involved. The present paper deals with the determination of the formation constants in the zinc-serine, zinc-histamine-serine, zinc-histamine-lysine, copper-serine, copper-histamine-serine, and copper-histamine-valine systems, which were still necessary to reach the reliable simulation required. The subsequent final distribution of histamine in plasma has thus been computed, and interpreted in terms of a possible role for zinc in assisting the histamine catabolism process. Further computer calculations simulating the increase of the zinc concentration in human blood plasma support this interpretation. The antagonizing role of copper against that of zinc has also been examined.