Polarized rat uterine epithelium in vitro: responses to estrogen in defined medium.

Previously described procedures for the culture of immature rat uterine epithelium (UE) allowed the cells to proliferate to confluence and develop morphological and functional polarity. The present study describes the transition from culture of UE cells in serum to a serum-free defined medium. This was accomplished with no significant alteration in the ability of UE cells to attain morphological and functional polarity. In defined medium, which contained estrogen (2.5 x 10(-9) M), UE cells proliferated to confluence, demonstrated separation of apical and basal plasma membrane domains, and displayed preferential secretion of proteins and proteoglycans from the apical surface. Apical secretions of polarized cultures contained complement component C3, the secreted portion of the immunoglobulin A receptor and the secretory glycoprotein, USP-1. The cell surface adhesion molecule, CAM 105, could be demonstrated at the apical cell surface. Expression of this profile of secretory and cell surface markers, representative of the in vivo estrogen response of immature rat UE cells, correlated with an in vitro state of non-receptivity of polarized UE cells toward blastocysts which remained viable and competent to attach. We conclude that the polarized UE cell that develops in the described defined medium expresses a phenotype similar to that which characterizes the in vivo uterine estrogen response.