ESTROGEN-RECEPTOR LEVELS IN ESTROGEN SENSITIVE CELLS IN CULTURE

Estradiol-17β (E2) receptor (R) levels of bona fide E2 sensitive cells were studied under a set of different cell culture conditions. E2R concentration in C811RAP cells in culture is affected by the concentration of serum in the culture medium. Removal of serum from the medium results in a swift decrease in the E2R concentration, reaching its lowest level after 6 h. Subculturing the cells in media containing different serum concentrations from 5 to 0.2% resulted in a sharp decrease in E2R concentration. The dose-response relationship between serum concentration and E2R level strongly suggests the presence in serum of (a) factor(s) responsible for the steady, high level of E2R observed in C811RAP cells growing in culture. The swift fall of the receptor level after serum withdrawal as well as the rapid recovery after exposure to serum could be explained assuming a very high turnover of the receptor, if the serum-borne factors act by stimulating the synthesis or impeding the degradation of E2R. Although the conditions under which these cells are grown in culture differ from those in situ in the animal host, it is under well defined conditions afforded by the in-culture environment that a direct evaluation of the role of putative E2R level modifiers may be properly studied and correlated with in vivo data. © 1979.