IMMUNOHISTOCHEMICAL DETECTION AND NORTHERN BLOT ANALYSIS OF ESTROGEN-RECEPTOR IN OSTEOBLASTIC CELLS

Expression of estrogen receptor (ER) was studied in MC3T3-El cells (mo use osteoblastic cell line), HOS TE85 cells (human osteosarcoma cell l ine), and primary osteoblastic cells derived from mouse calvaria with immunohistochemical techniques. The staining of ER was readily detecta ble in MC3T3-El cells, HOS TE85 cells, and primary osteoblastic cells by using a monoclonal anti-ER antibody that recognizes the DNA binding domain of ER. The immunoreactivity was distributed in the cytoplasm a s well as in the nuclei. 17beta-Estradiol (10(-8) M) did not alter thi s staining pattern. The expression of ER was confirmed by Northern blo t analysis using mt ER cDNA probe, which revealed a 6.5 kb band in MC3 T3-El cells and a 6.2 kb band in HOS TE85 cells. The mRNA level of ER was not altered by 17beta-estradiol (10(-8) M). The immunohistochemica l studies showed that ER was not detectable in all cells but in a smal l population of each cell type. This study is the first report to demo nstrate the presence of ER immunohistochemically, and our results sugg est the heterogeneity of ER expression among osteoblastic cells.