Influence of the carcinogenic oestrogen diethylstilboestrol on the intracellular calcium level in C6 rat glioma cells

The synthetic oestrogen diethylstilboestrol (DES) causes a dose-dependent elevation of the cytoplasmic Ca²⁺ concentration in C6 rat glioma cells. This Ca²⁺ rise is caused neither by Ca²⁺ influx nor by release from the Ca²⁺ stores of the endoplasmic reticulum. Therefore it seems likely that DES mobilizes Ca²⁺ from a mitochondrial source. The DES-induced Ca²⁺ signal is remarkably similar to the one induced by the tumour promotor thapsigargin. As this compound causes leakage of calcium from the endoplasmic reticulum it seems possible that DES induces a similar leakage from mitochondrial Ca²⁺ stores. It remains to be established whether the DES-mediated rise in intracellular calcium is causally related to the tumour-promoting properties of this compound.