Effect of direct current on cultured growth cartilage cells in vitro.

Cultured growth cartilage cells of young rabbits were stimulated by three levels (10, 1, and 0.1 microA) of constant direct current (DC). The effect of DC was examined by measuring the activities of proteoglycan synthesis (uptake of [35S]sodium sulfate and toluidine blue staining) and DNA synthesis (uptake of [3H]thymidine). DC increased syntheses of both proteoglycans and DNA when 1 microA (calculated current density of 1 microA/cm2) was applied for 3 days. A longer stimulation resulted in a larger difference between stimulated and unstimulated cells. Ten-microampere stimulation devitalized the cells, while 0.1 microA had no effect on cell activities.