1'he operation involving implantation of metal into bone is increasmg in clinical situation in recent years. Therefore the importance of cytotoxity test of the metals for bone cells is getting increased;however, the cffect on bone cells has not well been studied. The purpose of this study is to evaluate the effect of metal ions on osteoclast formation. Mouse bone marrow cells were cultured with prostaglandin E2 in the presence of metal salts, including nickel sulfate, cupric chloride, titanium

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... etrachloride, paradium chloride, and silver sulfate. After eight days, tartarate resistant acid phosphatase-positive multinuclcar cells were scored as osteoclasts. 1. Many tartarate resistant acid phosphatase-positive multinuclear cells were formed in the bone marrow cell culture with 1ptM prostaglandin Ez, A]1 of the metal salts inhibited the formation. The concentration of neckel sulfate, cupric chloride, titanium tetrachloride, paradium chloride, and silver sulfate needed for 50 % inhibition of the formation is 2.5, 5, 9, 70, and 150"M, respectively. 2. In microscopic observation, tartarate resistant acid phosphatase-positive multinuclear cells and fibroblast-like stroma cells disappeared in the culture by the addition of several kinds of metal salts, In the case of titianium tetrachloride, many osteoclast-like cells appeared to be degradating, while the stroma cells did not appear to be affected. 3. In scanning electron microscopic obsevation, the number of resorption pit formed by osteoclasts was shown to be reduced by the addition of the metal ions examined. In the case of the addition of titanium salt, many pits were smaller than those of without the addition. The results show that nickel ion, cupper ion, and paradium ion inhibited osteoclast formation, probably through the nonspesific manner. Titanium ion inhibited the formation, probably through the selective degradation of newly formed osteoclasts. This specific degradation by titanium may be involved in the stable settlement of titaniuni irnplant in NII-Electronic Mbrary