Effects of 2-formylpyridine monothiosemicarbazonato copper II on red cell components

1-Formylpyridine monothiosemicarbazonato copper II (CuL+) is readily taken up by red cells and is initially bound to glutathione and hemoglobin. Glutathione was depleted within 5 hr of incubation, presumably by oxidation mediated by CuL+ and O2 with concomitant generation of toxic oxygen species. Cupric ion was slowly transferred from CuL+ to hemoglobin within about 7 hr and hemoglobin was oxidized until the major form prevailing after 10 hr was alpha 2 beta 2+. Little increase in hemolysis due to addition of CuL+ dissolved in the radical scavenger dimethyl sulfoxide was observed with prolonged incubation. Strong inhibition of red cell hexokinase by CuL+ was observed when the enzymes in red cell lysates and hemoglobin-free red cell lysates were examined. CuL+ was also an effective inhibitor of yeast hexokinase. However, the inhibitory effect of CuL+ within the red cells was less pronounced. It is suggested that even though intracellular accumulation of CuL+ creates an oxidizing environment and is potentially capable of inhibiting thiol enzymes such as hexokinase, protective effects are exerted in the red cell by the presence of hemoglobin, of radical scavengers, and of high levels of enzymes that detoxify toxic oxygen species.