Abstract
The effects of bacterial lipopolysaccharide (Escherichia coli 0111:B4; LPS) on cytosolic free calcium were examined in cultured bovine endothelial cells. The effect of LPS on the cellular calcium response to vasopressin was also investigated. Intracellular calcium [Ca2+]i was determined using the fluorescent probe Fluo-3/AM and confocal microscopy. LPS caused a dose-dependent increase in [Ca2+]i. The calcium response to LPS was of the same magnitude when cells were studied in the absence of extracellular calcium suggesting that the effect of LPS is due mainly to a mobilisation of intracellular calcium stores. The cellular calcium response to vasopressin was completely abolished by LPS and vice versa. These results show that LPS evokes a rapid increase in intracellular free calcium in endothelial cells. This observation may contribute to an explanation for the early initial phase of the LPS-induced vascular hyporesponsiveness.

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