Zeolite A inhibits osteoclast-mediated bone resorption in vitro

The effects of Zeolite A on bone resorbing activity of highly purified avian osteoclasts were analyzed. The present study demonstrates that when 100 micrograms/ml of acid-treated Zeolite A is added to the media the number of pits per osteoclast is reduced 3-fold at 24 h after treatment. Secreted cathepsin B enzyme activity was also reduced 3-fold. A similar reduction in pit number per osteoclast was measured following 48 h of treatment with Zeolite A but there appeared to be less reduction of cathepsin B enzyme activity. The effects on pit number and cathepsin B protein activity were Zeolite dose dependent. The structure of the compound seemed to be responsible for the effects measured since compounds used to represent constituents of Zeolite A (silicon dioxide and aluminum chloride) failed to inhibit bone resorption or reduce the level of secreted cathepsin B enzyme activity. Thus the molecular architecture of Zeolite A or a derivative thereof appears to be important. In conclusion, the data indicate that Zeolite A can inhibit bone resorption. Together with previous data on osteoblasts, this might suggest a potential positive activity of intact Zeolite A or a partial substructure of Zeolite A on bone turnover.