Microtubule and plasmalemmal reorganization: acute response to estrogen

Dexamethasone blocks the rapid biological effects of 17beta-estradiol in the rat uterus without antagonizing its global genomic actions

Estrogens and glucocorticoids have opposing effects on the female reproductive tract, but the molecular basis for this antagonism is poorly understood. We therefore examined the biological and transcriptional programs induced by estrogens and glucocorticoids in the uterus of immature female rats. Estradiol 17beta (E2) rapidly induced morphological changes reminiscent of an acute inflammatory response, including infiltration of eosinophils, edema in the stroma and myometrium, and a decrease in the height of luminal epithelial cells, whereas dexamethasone (Dex) only altered stromal cell morphology. When coadministered with E2, Dex completely blocked the proinflammatory effects of E2. Surprisingly, examination of E2 and Dex effects on gene expression using cDNA microarrays and real-time PCR revealed that these hormones had similar effects on the expression of many genes and that very few genes displayed antagonistic regulation. Together, these results indicate strong discord between the early biologic and genomic actions of estrogens and glucocorticoids and highlight a complex regulatory role for glucocorticoids and GR in the mammalian uterus.

Regulation of the membrane estrogen receptor-alpha: role of cell density, serum, cell passage number, and estradiol

We used modified immunocytochemical conditions to quantify a membrane form of estrogen receptor-alpha (mERalpha) in a rat pituitary tumor cell line, GH3/B6/F10. We studied the regulation of mERalpha vs. levels of intracellular ERalpha (iERalpha) using our 96-well plate immunoassay. The anti-ERalpha antibody C542 was used to label the ERalpha (via conjugated alkaline phosphatase) in fixed permeabilized (for iERalpha) vs. nonpermeabilized cells (for mERalpha). Expression of mERalpha was highest at low cell densities (<1000 cells/well) and decreased significantly at densities where cellular processes touched, whereas the more abundant iERalpha increased with increasing cell density over the same range. Serum starvation for 48 h caused increases in mERalpha, whereas iERalpha levels showed no significant changes. A large decline in mERalpha and iERalpha levels with cell passage number was observed. Minutes after nM 17beta-estradiol (E2) treatment, a portion of the cells rounded up and detached from the culture plate, whereas nM cholesterol had no such effect. Although E2 treatment did not change mERalpha levels, the antigen was reorganized from a fine particulate to aggregation into asymmetric large granules of staining. That common culturing conditions favor down-regulation of mERalpha may explain the relatively few reports of this protein in other experimental systems.