Diethylstilbestrol increases intracellular calcium in lens epithelial cells

The effects of diethylstilbestrol (DES) on steady-state intracellular calcium concentration ([Ca(2+)](i)) and resting Ca(2+) influx were examined in primary cultures of bovine lens epithelial cells using conventional fluorometric techniques (Fura-2). At low concentrations (10 microM), DES usually induced relatively rapid increases in [Ca(2+)](i) that occurred over an interval of 10-50 s and that persisted for several minutes in the continued presence of the drug. In about 10% of the cells, cyclic oscillations in [Ca(2+)](i) were seen after adding 10 microM DES. At higher concentrations (100 microM), the drug induced more prolonged increases in [Ca(2+)](i) lasting several minutes. DES did not affect Mn(2+) quench determinations of resting Ca(2+) influx, and neither 100 microM GdCl(3), which blocked resting Ca(2+) influx, nor low [Ca(2+)](o) solutions substantially diminished the influence of DES on [Ca(2+)](i). Pretreatment of cells with the smooth endoplasmic reticulum Ca(2+) ATPase (SERCA) inhibitors cyclopiazonic acid (CPA) or thapsigargin completely abolished the effect of 10 microM DES on [Ca(2+)](i), while the IP(3) receptor blocker 2-aminoethoxydiphenyl borane (2-APB) had no effect. These results indicate that DES releases CPA-sensitive stores of intracellular Ca(2+), perhaps by inhibiting SERCA-dependent Ca(2+) sequestration.