Early elemental and ionic changes in cultured cells after stimulation with epidermal growth factor.

Stimulation of A431 cells (a human vulval epidermal cell line) with 50 ng/ml of epidermal growth factor (EGF) in the presence of 1.7 mM extracellular calcium produced a sharp and sustained rise in intracellular ionic Ca2+, increased elemental Na, decreased K and a rise in Ca. In the absence of extracellular calcium, the initial Ca2+ rise remained but the sustained elevation of intracellular Ca2+ was abolished, Na and K fluxes were variable and the Ca did not change. Increased Na and decreased K was marked at 2 minutes and returned to the control value after 60 minutes. The increase in Ca was an early event. Cells stimulated with EGF showed a pronounced morphological disruption, especially the mitochondria. The response of NR6/SA3 and NR6/DC7 cells (genetically engineered rodent fibroblast cell lines) to EGF stimulation was higher than that of the A431 cells, as was the resting cytoplasmic Ca2+. Untreated NR6/SA3 and NR6/DC7 cells possessed an increased Na/K ratio when compared with A431 cells.