Interaction between cadmium and zinc,copper, or lead in relation to the collagen and mineral content of embryonic chick bone in tissue culture

To investigate the interaction between Cd and Zn, Cu, or Pb in relation to the content of collagen and mineral in bone, femurs obtained from 9-day-old chick embryos were cultivated for 6 days by the Rollertube method. Zn prevented a decrease in collagen content caused by Cd, although Cu and Pb showed no such protective effect. Neither Zn, Cu, nor Pb prevented the decrease in mineral content caused by Cd. In the Cd-treated bone, the Cd content in the presence of Zn was larger than that in the absence of Zn. The Cd content in the cytosol fraction from Cd plus Zn-treated bones was larger than that from Cd-treated ones. When the cytosol fraction was applied to a Sephadex G-75 column, three Cd-containing peaks were observed. The first small peak (HM fraction) was eluted near the void volume, the second large peak (MT fraction) was metallothionein-like protein (MW = about 10,000), and the third peak contained low-molecular-weight (about 2500) compounds. The Cd content in the MT fraction from Cd plus Zn-treated bones was larger than that from Cd-treated ones. From these results it was concluded that a metallothionein-like protein, induced by Zn, served as a Cd scavenger and contributed to the protection against Cd-induced toxicity. On the other hand, when the 100,000g precipitate from cultured bone was solubilized and applied to a Sephadex G-75 column, one peak was observed in the position of the HM fraction. The activity of alkaline phosphatase in the HM fraction from Cd-treated bones was inhibited, but this inhibition was not observed in Cd plus Zn-treated ones. This finding suggests that competition between Cd and Zn in the HM fraction contributes, at least partly, to the protection against Cd-induced toxicity.