Variations in the levels of estrogen receptors in prolactin producing pituitary tumor cells.
The binding of [3H]-17 beta-estradiol in cells and cytoplasmic fractions of three different prolactin producing pituitary tumor lines was compared and found to vary widely. The concentration of estrogen receptors of the MtTW10 rat tumor line was high in early passages, but receptor levels decreased with subsequent passages in animals. Over a period of 12 months, the estrogen binding capacity in low speed supernatant fractions of cell homogenates decreased from 61.5 fmol [3H]-17 beta-estradiol per mg protein to less than 10 fmol [3H]-17 beta-estradiol per mg protein. A similar decrease in receptor concentration was found in MtTW10 cells which were adapted to in vitro culture. The concentration of receptor in low speed supernatant fractions of cultured GH3 rat tumor cells remained between 60 and 80 fmol [3H]-17 beta-estradiol per mg protein throughout the entire period of experimentation. In contrast, no high affinity receptors could be detected in similar fractions of the human pituitary cell line, 18-54, when cultured either in the presence or absence of serum. The Kd for the estradiol:receptor complex was determined to be 1.0 x 10(-10) M for receptors from MtTW10 cells and remained constant as the concentration of receptors declined. The receptors in both MtTW10 and GH3 cells were found to exist as 8s molecular species which are converted to 4s species by a temperature dependent process. The binding of estrogen to 8s and 4s receptors at 4 degrees C was shown to occur in the presence of 3 mg/ml of digitonin.
D000818:Animals; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D003593:Cytoplasm / Q000378:metabolism; D004054:Diethylstilbestrol / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D011960:Receptors, Estrogen; D004958:Estradiol; D004054:Diethylstilbestrol; D011388:Prolactin