Activation of calmodulin by the essential trace element chromium.

Chromium at very low concentrations is an essential trace element--at higher concentrations it is associated with contact dermatitis and other toxicity problems. Its ionic radius is just outside that of other metal cations which have been found to activate calmodulin in vitro. We found that chromium was able to activate calmodulin at two different concentration ranges--over the micromolar range (which would probably never be achieved in man) a small degree of activation was found--but a much greater activation (76% of the maximum possible) was also found at nanomolar concentrations of chromium. In welders, who work with stainless steel and who were not reporting any physical symptoms of chromium toxicity, red cell chromium levels were 28.2 +/- 3.3 nM (n = 22) compared to 7.5 +/- 0.7 nM (n = 11) for normal controls. Thus, the concentration of chromium experienced within the cell can be of the order which will activate calmodulin in vitro. The possibility exists, therefore, that inappropriate activation of calmodulin could be relevant to chromium biology possibly contributing to the symptoms of chromium toxicity.