Do the Copper Complexes of Histamine, Histidine and of Two H₂-Antagonists React with O⁻₂?

Abstract

The effects of cimetidine, ranitidine, histamine and histidine. as well as of their copper complexes, have been examined in an enzymic and chemical O⁻₂ generated systems. Copper complexes like CuZnSOD inhibited both the reduction of cytochrome c and NBT²⁺ in xanthine-xanthine oxidase systems, but their inhibitory action was due to a certain extent to the copper-induced inhibition of xanthine oxidase. EDTA abolished the inhibitory effect of all copper complexes studied. Luminol chemiluminescence in NADH,-PMS system was inhibited by CuZnSOD while it was enhanced by copper complexes. The copper-accelerating effect gradually increased up to about I μM Cu and decreased, reaching the control values up to 10 μM Cu. In the presence of low copper concentrations chemiluminescence was inhibited by CuZnSOD only, while in the presence of high copper concentrations it was inhibited by catalase and mannitol. but not by CuZnSOD. The ligands however, have been ineffective in the two O⁻_2; generated systems.

Key Words:

• Copper complexes
• luminol chemiluminescence
• superoxide
• xanthine oxidase
• histamine
• H₂-antagonists