Effects of steroids on human normal and otosclerotic osteoblastic cells: influence on thymidine and leucine uptake and incorporation.

Steroid hormones are able to influence the metabolism of bone tissue in vivo, but reports regarding their direct action on bone cells fail to agree. In this study, in vitro administration of 17 beta-estradiol, testosterone and corticosterone to normal and otosclerotic osteoblastic cells induced a drop in DNA synthesis in both populations, an increase in the neosynthesis of endocellular proteins in normal cells and a rise, mainly in proteins secreted into the medium, in otosclerotic cells. The fact that 3H-thymidine and 3H-leucine uptake were lower in otosclerotic than in normal cells suggests that the membrane permeability differs in the two populations and that steroids exert an influence on both isotope uptake and directly modulate DNA and protein synthesis.