Growth Regulation of L-929 Mouse Fibroblasts by Steroid Hormones and Anti-Hormones in Serum Containing and Serum Free Media

Abstract

Mouse L-929 fibroblasts contain 3 distinct steroid hormone receptors, RG for glucocorticosteroids, RA for androgens and RE for estrogens. There is no progesterone receptor. Sedimentation coefficient of receptors in low salt medium is ∿ 7–8 S and affinity for their respective hormones is very high (K_Deq ∿ 1 nM). RA binds androgens, anti-androgens (e.g. cyproteron acetate) and progesterone, and somewhat estradiol (but not DES, a synthetic estrogen). RE binds exclusively estrogens and anti-estrogens (e.g. tamoxifen), including DES. RA and RE do not bind glucocorticosteroids. RG binds glucocorticosteroids and progesterone, but neither androgens nor estrogens. At physiological concentrations, androgens or estrogens increase the rate of cell multiplication, and specific anti-hormones inhibit the related growth effect. In the presence of dexamethasone, cell multiplication is strongly decreased, and this effect can be abolished by addition of a new antiglucocorticosteroid, RU 486, of high affinity for RG. Moreover, plasma membrane seems affected by steroid hormones since cell adhesiveness is increased in the presence of androgens or estrogens but decreased in the presence of glucocorticosteroids, effects which are also abolished by the corresponding anti-hormones. These observations were made using culture medium supplemented with charcoal extracted calf serum, and were confirmed in serum free culture medium (SF). The doubling time in SF medium is longer, 24 h instead of 18 h. However, after long term cultures in SF medium (4 months) no change in receptor concentrations was observed and the 18 h doubling time was immediately restored in serum containing culture medium.