Flow cytometric detection and binding studies of human endometrial stromal cell epidermal growth factor receptor in monolayer culture : influence of progesterone

Epidermal growth factor (EGF) has been shown to modulate endometrial differentiation in vivo and in vitro. Therefore, endometrial stromal cell EGF receptors were characterized in intact endometrial stromal cells, cultured in vitro. The methods used for characterization were flow cytometry, binding and displacement studies, and gel electrophoresis followed by autoradiography. In flow cytometry the histogram of labelled stromal cells was identical to Caski cells, which served as a positive control. EGF binding revealed the typical binding hierarchy for EGF receptors. The Scatchard analysis showed a curvilinear plot with a calculated dissociation constant of 0.36 nM for high affinity binding sites. In autoradiography a band of approximately 170 kDa was visualized corresponding to the known size of the EGF receptor. The intensity of this band was increased by pretreatment of stromal cells with 10 nM progesterone for 4 days. Furthermore, stimulation with progesterone led to an increase in specific EGF binding activity of stromal cells by 21% compared to control. These data indicate that intact stromal cells in monolayer culture maintain specific EGF receptors, which are up-regulated by progesterone.