Epidermal growth factor induces intracellular Ca 2+ oscillations in microvascular endothelial cells

An increase in intracellular Ca 2+ concentration ([Ca 2+ ] i ) may play a role in the proliferative effect of several growth factors. In this study, the changes in [Ca 2+ ] i elicited by epidermal growth factor (EGF) in rat cardiac microvascular endothelial cells (CMEC) have been investigated by using fura‐2 conventional and confocal microscopy. A large heterogeneity in the latency and in the pattern of the Ca 2+ response was found at each dose of EGF (2.5–100 ng/ml), whereas some cells displayed a non‐oscillatory behavior and others exhibited a variable number of Ca 2+ oscillations. On average, the fraction of responsive cells, the total number of oscillations and the duration of the Ca 2+ signal were higher at around 10 ng/ml EGF, while there was no dose‐dependence in the lag time and in the amplitude of the [Ca 2+ ] i increase. EGF‐induced Ca 2+ spikes were abolished by the tyrosine kinase inhibitor genistein, but not by its inactive analogue daidzein, and by the phospholipase C blocker NCDC. Only 1–2 transients could be elicited in Ca 2+ ‐free solution, while re‐addition of extracellular Ca 2+ recovered the spiking activity. The oscillatory signal was prevented by the SERCA inhibitor thapsigargin and abolished by the calcium entry blockers Ni 2+ and La 3+ . Moreover, EGF‐induced Ca 2+ transients were abolished by the InsP 3 receptor blocker caffeine, while ryanodine was without effect. Confocal imaging microscopy showed that the Ca 2+ response to EGF was localized both in the cytoplasm and in the nucleus. We suggest that EGF‐induced [Ca 2+ ] i increase may play a role in the proliferative action of EGF on endothelial cells. © 2002 Wiley‐Liss, Inc.