Endocrinology, Vol 124, 2837-2843, Copyright © 1989 by Endocrine Society

ARTICLES

Serum and monohydroxytamoxifen inhibit progesterone receptor concentrations in primary rat uterine cells grown in serum-free medium

TL Greco and J Gorski
Department of Biochemistry, University of Wisconsin, Madison 53706.

Uterine cells dispersed from immature rat uteri were grown in culture in serum-free medium supplemented with insulin (5 micrograms/ml), transferrin (5 micrograms/ml), and selenous acid (5 ng/ml; ITS). Cells were grown to a confluent monolayer and had a fibroblastic appearance, similar to cells cultured in the presence of 10% serum [horse-fetal calf (6:1), stripped three times with dextran-coated charcoal]. However, estrogen receptor and progesterone receptor (PgR) concentrations were higher in cells grown in serum-free medium than in cells grown in serum. Uterine cells grown in ITS contain PgR levels that are near maximum (927 +/- 168 fmol/mg protein), and estradiol (0.1 nM; 24 h) causes a 10-50% increase in PgR. Addition of serum or monohydroxytamoxifen for 24 h decreases PgR levels by about 50%, and estrogen can completely overcome the inhibition caused by either serum or monohydroxytamoxifen. Our data suggest that PgR levels may be down- regulated by a component of serum.