17 beta-estradiol increases Ca(2+) influx and down regulates interleukin-2 receptor in mouse thymocytes

The influx of Ca(2+) across the T lymphocyte membrane is an essential triggering signal for activation and proliferation by an antigen. The aim of this study was to determine if Ca(2+) influx through estradiol receptor (ER) operated channels of Ca(2+) entry induced activation of lymphoid cells. Mouse thymocytes were incubated with 17 beta-estradiol (E) and in the presence or absence of the mitogen, phytohemagglutinin (PHA). Despite evidence of an enhanced binding of E to ER on thymocyte membranes, and an E dose-related influx of Ca(2+), there was a consistent down regulation of IL-2 receptor expression (P < 0.001). Incubation of thymocytes with PHA enhanced IL-2 receptor expression although the down regulatory effect of E was still evident. The results suggest that the Ca(2+) channel activated by E may have a down regulatory effect on the IL-2 receptor in thymus cells leading to the dampening of cell activation process.