Bidirectional regulation of osteoclast function by nitric oxide synthase isoforms

Immunocytochemistry and Northern blotting during bidirectional regulation of osteoclasts function by nitric oxide, shows the presence of the constitutive calcium-sensitive nitric oxide synthase (cNOS) isoform in normal rat osteoclasts, and in human preosteoclast cell line. The presence of inducible (I) NOS isoform was also demonstrated. A basal level of transcript was observed in human preosteoclast line. Osteoclasts function may require continuous increases in NO production by cNOS against a basal inhibitory background activity of the iNOS isoform.