0023-6152

AA00697606

4486551

The fish scales are well known as a major source of internal calcium storage. Therefore, we developed an original assay system using goldfish scales in which both osteoclasts (bone resorption cells) and osteoblasts (bone formation cells) coexist. In our bioassay system, we utilized the activities of tartrate–resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP) as respective indicators of each activity in osteoclasts and osteoblasts. Using this bioassay system, the influence of cadmium chloride (CdCl_2) on osteoclastic and osteoblastic activities in the scales of goldfish was examined in an in vivo experiment. Goldfish were kept in tap water containing CdCl_2 (10^–7 M) for 2 days. TRAP activity in the scales of goldfish decreased with 2 days of exposure to CdCl_2. This inhibitory effect for osteoclasts continued even at 4 days of exposure to CdCl2. In the case of osteoblasts, CdCl2 inhibited ALP activity in the goldfish scales at 4 days after exposure, although ALP activity in the goldfish scales had not changed after 2 days of exposure to CdCl_2. In in vitro cultured goldfish scales, we previously reported that ALP activity decreased after exposures of 64 and 96 hrs, although their activities did not change after 6, 18, and 36 hrs. These results were supported by our in vivo experiment. This is the first report to indicate that both osteoclasts and osteoblasts in fish were suppressed by cadmium (Cd) treatments in vivo. Considering both in vivo and in vitro experiments, we concluded that Cd inhibited both osteoclastic and osteoblastic activities in goldfish. This suggests that Cd leads to a disturbed calcium metabolism and then induces bone anomalies.