Estradiol binding to cell surface raises cytosolic free calcium in T cells

The Fura-2 method is used to examine a possible action of 17β-estradiol (E 2) on [Ca 2+] i of splenic T cells isolated from female C57BL/10 mice. E 2 concentrations between 10 fM and 10 nM induce a rapid and dose-dependent increase in [Ca 2+] i due to Ca 2+ influx and release of Ca 2+ from intracellular stores. Ca 2+ influx is mediated by Ca 2+ channels which are completely blockable by Ni 2+ and partly by nifedipine. The antiestrogen tamoxifen does not inhibit the E 2-induced rise in [Ca 2+] i. Ca 2+ influx and Ca 2+ release from intracellular stores is also inducible by plasma membrane impermeable E 2 conjugated to BSA. E 2-BSA-FITC binds to the surface of T cells of both the CD4 + and CD8 + subset. Our data suggest a novel E 2-signalling pathway in T cells which is not mediated through the classical nuclear estrogen receptor response but rather through putative plasma membrane receptors for E 2.