Differential effects of monovalent, divalent and trivalent metal ions on rat brain hexokinase.

The effects of monovalent (Li+, Cs+) divalent (Cu2+, Ca2+, Sr2+, Ba2+, Zn2+, Cd2+, Hg2+, Pb2+, Mn2+, Fe2+, Co2+, Ni2+) and trivalent (Cr3+, Fe3+, Al3+) metals ions on hexokinase activity in rat brain cytosol were compared at 500 microM. The rank order of their potency as inhibitors of brain hexokinase was: Cr3+ (IC50 = 1.3 microM) greater than Hg2+ = Al3+ greater than Cu2+ greater than Pb2+ (IC50 = 80 microM) greater than Fe3+ (IC50 = 250 microM) greater than Cd2+ (IC50 = 540 microM) greater than Zn2+ (IC50 = 560 microM). However, at 500 microM Co2+ slightly stimulated brain hexokinase whereas the other metal ions were without effect. That inhibition of brain glucose metabolism may be an important mechanism in the neurotoxicity of metals is suggested.