{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,8]],"date-time":"2026-07-08T22:20:40Z","timestamp":1783549240782,"version":"3.55.0"},"reference-count":0,"publisher":"National Academy of Sciences","issue":"7","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[1988,4]]},"abstract":"<jats:p>Estrogens play a crucial role in the development of postmenopausal osteoporosis. However, the mechanism by which estrogens exert their effects on bone is unknown. To examine possible direct effects of 17 beta-estradiol on bone-forming cells, we used pure rat osteoblast-like cells in vitro as a model. Osteoblast-like cells prepared from calvaria of newborn rats were cultured serum-free in methylcellulose-containing medium for 21 days. Osteoblast-like cells proliferate selectively into clonally derived cell clusters of spherical morphology. 17 beta-Estradiol at concentrations of 0.1 nM and 1 nM enhanced osteoblast-like cell proliferation by 41% and 68% above vehicle-treated controls. The biologically inactive stereoisomer 17 alpha-estradiol (same concentrations) had no effect. Moreover, the antiestrogen tamoxifen abolished the stimulation of osteoblast-like cell proliferation by 17 beta-estradiol. After 21 days of culture, RNA was prepared and analyzed in a dot-hybridization assay for the abundance of pro alpha 1(I) collagen mRNA. Steady-state mRNA levels were increased in cultures treated with 17 beta-estradiol in a dose-dependent manner with maximal stimulation at 1 nM and 10 nM. At the same concentrations, the percentage of synthesized protein (labeled by [3H]proline pulse) that was digestible by collagenase was increased, indicating that 17 beta-estradiol acts at pretranslational levels to enhance synthesis of bone collagen. These data show that the osteoblast is a direct target for 17 beta-estradiol.<\/jats:p>","DOI":"10.1073\/pnas.85.7.2307","type":"journal-article","created":{"date-parts":[[2006,5,31]],"date-time":"2006-05-31T06:51:57Z","timestamp":1149058317000},"page":"2307-2310","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":140,"title":["Enhanced osteoblast proliferation and collagen gene expression by estradiol."],"prefix":"10.1073","volume":"85","author":[{"given":"M","family":"Ernst","sequence":"first","affiliation":[{"name":"Department of Medicine, University Hospital of Zurich, Switzerland."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"C","family":"Schmid","sequence":"additional","affiliation":[{"name":"Department of Medicine, University Hospital of Zurich, Switzerland."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"E R","family":"Froesch","sequence":"additional","affiliation":[{"name":"Department of Medicine, University Hospital of Zurich, Switzerland."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[1988,4]]},"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.85.7.2307","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,13]],"date-time":"2022-04-13T12:38:59Z","timestamp":1649853539000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/full\/10.1073\/pnas.85.7.2307"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1988,4]]},"references-count":0,"journal-issue":{"issue":"7","published-print":{"date-parts":[[1988,4]]}},"alternative-id":["10.1073\/pnas.85.7.2307"],"URL":"https:\/\/doi.org\/10.1073\/pnas.85.7.2307","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[1988,4]]},"assertion":[{"value":"1988-04-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}