标题：Influence of Poisonous Metals on the Bone Metabolism. IV. The Effect of Cadmium on Collagen Synthesis and Degradation of Embryonic Chick Bone in Tissue Culture
摘要：In order to clarify whether the decrease in the hydroxyproline content of cadmium-treated cultured bone is due to an inhibition of collagen synthesis or a stimulation of its degradation, femurs from 9-day chick were cultivated for six days by the roller-tube method, and CdCl2 was added to the culture medium in the 0.2 to 30 ppm concentration range as Cd2+. The hydroxyproline content of the whole bone was decreased by concentrations of cadmium exceeding 1 ppm. When the whole bone was divided into the cartilage ends and bone shafts, cadmium produced a decrease in the hydroxyproline content of the former without any apparent effect on the latter. To investigate the effects of cadmium on collagen synthesis and degradation, the bones and media after culture and the uncultured bones were analyzed for hydroxyproline. The synthesis of hydroxyproline was significantly inhibited by levels of cadmium above 1 ppm. The release of hydroxyproline from the bone into the medium was inhibited by levels of cadmium above 0.2 ppm, but the percentage of the hydroxyproline released into the medium (relative to the total found in the bone and medium) was unaffected by cadmium. These results show that the decrease in hydroxyproline content of cadmium-treated bone may be due to the inhibition of collagen synthesis. On the other hand, when the bone shafts were treated with bacterial collagenase, cadmium had no effect on the hydroxyproline content but caused a decrease in the calcium content of collagenase-undigestible fraction which contained 95% of the total cadmium incorporated into the bone shafts. Cadmium seems to coexist with calcium phosphate on the basis of an elemental analysis of calcified positions of bone shafts using an energy dispersive X-ray microanalyzer.
