BONE TOXICITY OF LOCALLY APPLIED AMINOGLYCOSIDES

The effect of tobramycin on osteoblasts was studied. Osteoblastlike ce lls from the MG-63 human osteosarcoma cell line were grown in antibiot ic-free media and exposed to concentrations of tobramycin: first at or der of magnitude intervals between 0 and 10,000 mu g/ml, and then at c loser intervals between 100 and 1,000 mu g/ml to more accurately defin e toxic levels. Cell number and H-3-thymidine incorporation at 0, 24 a nd 72 h were determined. Similarly, primary cultures of rat osteoblast s were exposed to the same concentrations of tobramycin to confirm the validity of the MG-63 cell line as a model for nontransformed cells. The results of this study demonstrate that local levels of tobramycin of less than or equal to 200 mu g/ml have little or no effect on osteo blast replication. Concentrations of 400 mu g/ml significantly decreas ed cell replication, and concentrations of 10,000 mu g/ml caused cell death. Results obtained with primary rat osteoblast cultures were simi lar to those obtained from the MG-63 cultures at the tested tobramycin concentrations.