Mechanism of estrogens‐induced increases in intracellular Ca 2+ in PC3 human prostate cancer cells

BACKGROUND The effect of estrogens (diethylstilbestrol [DES], 17β‐estradiol) on intracellular Ca 2+ concentrations ([Ca 2+ ] i ) in hormone‐insensitive PC3 human prostate cancer cells was examined. METHODS [Ca 2+ ] i changes in suspended cells were measured by using the Ca 2+ ‐sensitive fluorescent dye fura‐2. RESULTS Estrogens (1–20 μM) increased [Ca 2+ ] i concentration‐dependently with DES being more potent. Ca 2+ removal inhibited 50 ± 10% of the signal. In Ca 2+ ‐free medium, pretreatment with 20 μM estrogens abolished the [Ca 2+ ] i increases induced by 2 μM carbonylcyanide m ‐chlorophenylhydrazone (CCCP, a mitochondrial uncoupler) and 1 μM thapsigargin (an endoplasmic reticulum Ca 2+ pump inhibitor), but pretreatment with CCCP and thapsigargin did not alter DES‐induced Ca 2+ release and partly inhibited 17β‐estradiol‐induced Ca 2+ release. Addition of 3 mM Ca 2+ increased [Ca 2+ ] i in cells pretreated with 1– 20 μM estrogens in Ca 2+ ‐free medium. Pretreatment with 1 μM U73122 to block phospholipase C‐coupled inositol 1,4,5‐trisphosphate formation did not alter estrogens‐induced Ca 2+ release. The effect of 20 μM estrogen on [Ca 2+ ] i was not affected by pretreatment with 0.1 μM estrogens. CONCLUSIONS Estrogen induced significant Ca 2+ release and Ca 2+ influx in an inositol 1,4,5‐trisphosphate‐independent manner in PC3 cells. These effects of estrogens on Ca 2+ signaling appear to be nongenomic. Prostate 47:141–148, 2001. © 2001 Wiley‐Liss, Inc.