Inhibitory effects of serum and stimulatory effects of estrogen on prolactin mRNA levels in GH3 rat pituitary tumor cells.
We investigated the effects of serum and estrogen on prolactin (PRL) mRNA accumulation in GH3 cells under different cell culture conditions. Hybridization analysis of GH3 cellular RNA indicated that PRL mRNA levels decreased more than 20-fold in cells cultured for 1 week in medium containing dextran-charcoal-treated serum (stripped serum). No effects on actin mRNA levels were observed under these conditions. Furthermore, this inhibition of PRL mRNA accumulation depended on the concentration of stripped serum in the medium. Although incubation in stripped-serum medium inhibited cell growth, these culture conditions did not appear to irreversibly affect the GH3 cell population. These data indicate that a potent inhibitor of PRL mRNA accumulation is present in stripped serum. GH3 cells grown in stripped-serum medium were shown to be responsive to estrogen. Treatment of these cells with 10(-9) M estradiol resulted in a 6.6-fold stimulation of PRL gene expression. However, estrogen had no effect on cell growth under these conditions, suggesting that estrogen stimulates PRL gene expression and cell proliferation by independent mechanisms.
Rhode
P R
PR
Department of Chemistry, California Institute of Technology, Pasadena 91125.
Gorski
J
J
D000818:Animals; D001769:Blood; D002455:Cell Division; D004967:Estrogens / Q000502:physiology*; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000096:biosynthesis; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D011388:Prolactin / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014407:Tumor Cells, Cultured
D004967:Estrogens; D012333:RNA, Messenger; D011388:Prolactin; D013006:Growth Hormone