Nongenomic effects of an anti-idiotypic antibody as an estrogen mimetic in female human and rat osteoblasts
✍ Scribed by Dalia Sömjen; Fortüne Kohen; Michèle Lieberherr
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 351 KB
- Volume
- 65
- Category
- Article
- ISSN
- 0730-2312
No coin nor oath required. For personal study only.
✦ Synopsis
We investigated the early effects of the anti-idiotypic antibody (clone 1D 5 ), which recognized the estrogen receptor (ER), on cytosolic free calcium concentration ([Ca 21 ]i) and its long term effects on creatine kinase (CK) specific activity in female human and rat osteoblasts. These actions were compared to the known membrane and genomic effects of 17b estradiol (E 2 ). Like E 2 , clone 1D 5 increased within 5 s [Ca 21 ]i in both cell types by two mechanisms: 1) Ca 21 influx through voltage-gated Ca 21 channels as shown by using EGTA, a chelator of extracellular Ca 21 , and nifedipine, a Ca 21 channel blocker; 2) Ca 21 mobilization from the endoplasmic reticulum as shown by using phospholipase C inhibitors, such as neomycin and U-73122, which involved a Pertussis toxin-sensitive G-protein. Clone 1D 5 and E 2 stimulated CK specific activity in human and rat osteoblasts with ten fold higher concentrations than those needed for the membrane effects (0.1 µg/ml and 10 pM, respectively). Both effects were gender-specific since testosterone and 5a-dihydotesterone were uneffective. Tamoxifen and Raloxifene, two estrogen nuclear antagonists, inhibited CK response to 1D 5 and E 2 and Ca 21 response to 1D 5 , but not Ca 21 response to E 2 . By contrast, (Fab8) 2 dimer, a proteolytic fragment of 1D 5 with antagonist properties, inhibited both membrane and genomic effects of 1D 5 and E 2 . In conclusion, these results imply that clone 1D 5 has an estrogen like activity both at the membrane and nuclear levels in female human and rat osteoblasts. 1D 5 must therefore interact with membrane binding sites, penetrate the cells, and reach the nuclear receptors by an as yet uncharacterized mechanism.