Effect of YM598, a selective endothelin ETA receptor antagonist, on endothelin-1-induced bone formation

We investigated the effect of endothelin-1 on bone formation in vitro and in vivo, and the effect of YM598, a novel selective endothelin ET(A) receptor antagonist, on endothelin-1-induced responses. In in vitro studies, the effect of endothelin-1 on cellular responses was investigated by measuring intracellular Ca(2+) levels, cell growth and alkaline phosphatase activity in the mouse osteoblast-like cell line MC3T3-E1. In in vivo studies, the effect of endothelin-1 on bone morphogenetic protein-2-induced ectopic bone formation in rats was investigated. A carrier containing bone morphogenetic protein-2 with or without endothelin-1 was subcutaneously implanted over the thorax, and the tissue (carrier) calcium content 3 weeks after implantation was evaluated. The inhibitory effect of YM598 on these responses was also investigated. In the in vitro studies, endothelin-1 (10(-13) to 10(-6) M) significantly increased intracellular Ca(2+) concentration, DNA synthesis and cell number in a concentration-dependent manner, while significantly decreasing alkaline phosphatase activity. YM598 (10(-12) to 10(-4) M) significantly inhibited these increases, as well as the decrease in alkaline phosphatase activity, in a concentration-dependent manner. In the in vivo studies, the tissue calcium content 3 weeks after carrier implantation was significantly higher in the group that received both bone morphogenetic protein-2 and endothelin-1 than in the group receiving bone morphogenetic protein-2 alone. Chronically administered YM598 (1 mg/kg/day) marginally inhibited this endothelin-1-potentiated ectopic bone formation. These results suggest that endothelin-1 may induce bone formation via endothelin ET(A) receptors in vitro and in vivo.