Benz[a]anthracene Decreases Plasma Calcium Levels Resulting from Influence of Scale Osteoclastic and Osteoblastic Activities in Goldfish

In the present study, the effects of polycyclic aromatic hydrocarbons (PAHs) on plasma calcium, osteoblasts and osteoclasts were investigated. Goldfish were intraperitoneally injected with benz[a]anthracene (BaA) (5μg/g body weight) (around 10-5 M). BaA induced hypocalcemia at 24 and 48 h and thereafter the level recovered to control levels at 72 h. Goldfish scales possess both osteoclasts (bone resorption cells) and osteoblasts (bone forming cells). The marker e nzyme activity (tartrate-resistant acid phosphatase: TRAP) of osteoclasts in goldfish scales decreased at 12 and 24 h after BaA injection. In BaA injected goldfish scales, the marker enzyme (alkaline phosphatase, ALP) gradually decreased at 48 and 72 h. In addition, 4-hydroxybenz[a]anthracene (4-OHBaA) that is one of the metabolites of BaA by conversion enzyme (P4501A1) was detected in the bile of goldfish at 12, 24, 48, and 72 h after administration of BaA to goldfish. We have recently found the toxicity of monohydroxylated polycyclic aromatic hydrocarbons (OHPAHs), metabolites of PAHs, in bone metabolism. We reported that 4OHBaA suppressed both TRAP and ALP activities in the cultured scales of goldfish. Therefore, it was prob able that 4-OHBaA metabolized from BaA has toxicity for osteoclasts and osteoblasts in goldfish. These phenomena are a cause of the disruption of the bone metabolism and the induction of spinal deformities.