Diphenylamine-2-carboxylate (DPC) reduces calcium influx in a mouse mandibular cell line (ST885).

Non-selective cation channels are found in many diverse cell types and have been proposed as a potential entry path for Ca2+. ST885 cells contain large numbers of these channels which are active in the resting cell. We have used Fura-2 to monitor changes in intracellular free Ca2+ ([Ca2+]i) in response to step changes in extracellular Ca2+ ([Ca2+]o). We found that DPC, a blocker of the non-selective cation channel in these cells, caused a reduction of approximately 50% in the rate of rise in [Ca2+]i following a step increase in [Ca2+]o. Since our experiments demonstrate that this phenomenon is not due to DPC blockade of Cl- channels, the Na+/Ca2+ exchanger or cyclooxygenase, we conclude that it is attributable to a direct effect of DPC on the non-selective cation channel. It thus appears that the non-selective cation channel is a significant pathway for basal Ca2+ entry in these cells.