Agonist-induced calcium and oxidative stress responses in endothelial cells

[Ca2+](i) (Cytosolic [Ca2+]) and OS (oxidative stress) were measured simultaneously in calf pulmonary artery endothelial cells using fura-2 and carboxy-2',7'-dichlorodihydrofluorescein. ATP stimulated a [Ca2+](i) increase that was followed a few seconds later by an increase in OS. Pre-exposure to 5 muM H2O2 potentiated these responses to ATP. Elevating or removing extracellular Ca2+ increased or reduced the [Ca2+](i) response to ATP and caused parallel changes in the OS response, suggesting that this response was a consequence of the [Ca2+](i) response. inhibition of mitochondria with rotenone or antimycin A affected the responses but not in a manner that allowed a simple interpretation of the role of mitochondria. These data show an initimate connection between [Ca2+](i) and OS that can be modulated by low levels of exogenously applied OS, allowing the possibility of positive feedback.