EARLY ELEMENTAL AND IONIC CHANGES IN CULTURED-CELLS AFTER STIMULATIONWITH 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 extr acellular 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 b ut the sustained elevation of intracellular Ca2+ was abolished, Na and K fluxes were variable and the Ca did not change. Increased Na and de creased K was marked at 2 minutes and returned to the control value af ter 60 minutes. The increase in Ca was an early event. Cells stimulate d with EGF showed a pronounced morphological disruption, especially th e mitochondria. The response of NR6/SA3 and NR6/DC7 cells (genetically engineered rodent fibroblast cell lines) to EGF stimulation was highe r than that of the A431 cells, as was the resting cytoplasmic Ca2+. Un treated NR6/SA3 and NR6/DC7 cells possessed an increased Na/K ratio wh en compared with A431 cells.