Biological action of epidermal growth factor and its functional receptors in normal mammary epithelial cells.
Normal murine mammary epithelial cells possessed the capacity to bind epidermal growth factor (EGF) in a specific and saturable manner. Scatchard plot analysis showed a curvilinear pattern. Assuming that this is not due to negative cooperativity of EGF binding, the data suggest the presence of two classes of receptors with a high and a low affinity: Kd values = 1 x 10(-10)M and 3.6 x 10(-9)M, respectively. The number of high- and low-affinity receptors was estimated to be 800 per cell and 8,600 per cell, respectively. The occupancy of EGF receptors for a half-maximal stimulation of DNA synthesis or inhibition of casein synthesis was about 10% and 6% of total receptors, respectively. A potent tumor promoter, 12-O-tetradecanoylphorbol 13-acetate, acted synergistically with EGF in terms of stimulation of DNA synthesis but not in terms of inhibition of casein synthesis when the two agents were added at a suboptimal concentration. The presence of the tumor promoter increased the amount of EGF bound to mammary cells in culture and also decreased a loss in the amount of EGF in the culture medium. These results indicate that mammary epithelial cells possess functional receptors for EGF, which are modulated by the tumor promoter.
D000818:Animals; D004815:Epidermal Growth Factor / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D066246:ErbB Receptors; D005260:Female; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D011247:Pregnancy; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D013755:Tetradecanoylphorbol Acetate