Figure 1.

A low androgen concentration specifically stimulates the S-phase entry of NIH3T3 cells. (A) Quiescent fibroblasts on coverslips were left untreated (○) or treated (•) for the indicated times with 0.001 nM R1881. After in vivo labeling with 100 μM BrdU, the cells were fixed, permeabilized, and stained for BrdU incorporation. DNA synthesis was calculated by the formula: percentage of BrdU-positive cells = (number of BrdU-positive cells/number of total cells) × 100. (B) The cells were left untreated or treated with the indicated compounds, labeled with BrdU, and were fixed and stained after 18 h. DNA synthesis was calculated as in A. Different experiments were performed and multiple coverslips were analyzed. The means and SEM are shown. (C) Lysates from quiescent NIH3T3, LNCaP, MCF-7, and T47D cells were immunoblotted with the antibodies against the indicated receptors. Endogenous AR in NIH3T3 cells was revealed by two different antibodies (either C-19 or N-20). The optical density/mm² measured by densitometric analysis of blot with C-19 anti-AR antibody was 6.12 and 0.47 for AR expressed in LNCaP and NIH3T3 cells, respectively. In the lowest section of C, lysates from primary fibroblasts (mouse fibroblasts, MF, or mouse embryo fibroblasts, MEF, both at second passage) were immunoblotted with the C-19 anti-AR antibody.