Expression of voltage-gated calcium channels correlates with PDGF-stimulated calcium influx and depends upon cell density in C3H 10T1/2 mouse fibroblasts.
Platelet derived growth factor (PDGF) mobilizes multiple calcium pools in the C3H 10T1/2 mouse fibroblast, including a sustained influx of extracellular calcium. We have used the whole cell patch-clamp technique to directly test for a role of plasma membrane calcium channels in this influx. Whole-cell patch-clamp recordings revealed a voltage-gated calcium channel with gating properties consistent with a 'T-type' designation. This phenotype of the C3H 10T1/2 fibroblasts was dependent upon the cell density in culture. The fraction of cells expressing calcium channels was low (< 10%) in subconfluent culture but rose to approximately 50% as the cells established a confluent monolayer. The magnitude of the PDGF-stimulated sustained calcium influx component measured using Fura-2 increased in parallel with the expression of calcium current. We interpret these results to support the hypothesis that T-type voltage-gated calcium channels contribute to the PDGF-stimulated intracellular calcium signals in these cells.