PTH INDUCES MODIFICATION OF TRANSDUCTIVE EVENTS IN OTOSCLEROTIC BONE CELL-CULTURES

We studied the effect of PTH (10-100 nM) on transductive mechanisms (a denylate cyclase activity, Ca2+ metabolism, IP3 levels) in cell cultur es derived from normal and otosclerotic human bone fragments. The cult ured cells were osteoblast-like but with calcitonin-receptors still pr esent and with PTH receptors coupled with the adenylate cyclase system . The results showed that PTH activated adenylate cyclase and increase d the intracellular Ca2+ levels with qualitative and quantitative diff erences between the two cellular populations. In particular, otosclero tic cells responded less to hormone stimulation, which is in accord wi th the current hypothesis of a desensitization of the receptor/enzyme complex associated with the pathological status.