QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Electronic Letters to:

ARTICLES: V. Krishnan, H. A. Bullock, B. C. Yaden, M. Liu, R. J. Barr, C. Montrose-Rafizadeh, K. Chen, J. A. Dodge, and H. U. Bryant The Nongenotropic Synthetic Ligand 4-Estren-317-diol Is a High-Affinity Genotropic Androgen Receptor Agonist Mol Pharmacol 2005; 67: 744-748 [Abstract] [Full text] [PDF]

eLetters: Submit a response to this article

Electronic letters published:

Primary versus indirect effects of estren

Michael Centrella, Thomas L. McCarthy and Richard B. Hochberg   (1 December 2004)

Author's Response

Gary Krishnan   (1 December 2004)

Primary versus indirect effects of estren 1 December 2004
Michael Centrella, professor Yale University School of Medicine, Thomas L. McCarthy and Richard B. Hochberg Send letter to journal: Re: Primary versus indirect effects of estren michael.centrella{at}yale.edu Michael Centrella, et al.	The article by Krishnan and colleagues, pre-published online on November 22, 2004 in Molecular Pharmacology (1), carefully shows that 4- estren-3alpha,17beta-diol, commonly termed estren, has potent androgenic effects in vitro and in vivo. The authors state that their work reveals a previously unidentified genotropic action of estren by androgen receptor. We feel that this somewhat inadequately acknowledges the results that we reported earlier (2). Indeed, using direct and indirect biochemical and biological assays, and estrogen and androgen receptor antagonists, we established the same androgen receptor dependency in primary cultures of osteoblasts, a model similar to one where Kousteni and colleagues first identified the skeletal effects of this compound (3,4). We were gratified to note that the binding affinities by estren for estrogen and androgen receptors, as determined by Krishnan and colleagues, were essentially identical to those that we measured, although we each used different receptor sources. The authors stated simply our finding that the conversion of estren to 19-nortestosterone was responsible for some of the androgenic effects of estren. Indeed, we showed that estren is rapidly and facilely converted to the potent androgen, 19-nortestosterone, by 3alpha- hydroxysteroid dehydrogenase, an activity that is expressed ubiquitously by multiple enzyme families (5,6). It is clear from both of our efforts that estren has a 5- to 10-fold higher affinity for androgen receptor relative to estrogen receptor. However, we feel it is important to note again that its androgen receptor affinity is nearly 200-fold less than dihydrotestosterone, and its estrogen receptor affinity is nearly 300-fold less than estradiol. In contrast, 19-nortestosterone is an avid ligand for the androgen receptor, with an affinity 100-fold greater than estren. To us, this predicts that high, pharmacological levels of estren would be required for androgenic activity relative to its potent metabolite, 19- nortestosterone. Even if some androgenic effects by estren could occur through direct sex steroid receptor activation, the current report does not eliminate the likelihood or contribution of its metabolism to 19- nortestosterone. Therefore, although this manuscript does not yet establish if estren is a primary or indirect effector of sex steroid receptor activity, we can be certain that it confirms that its androgenic actions contribute greatly to its function in vivo. Michael Centrella, Thomas L. McCarthy, and Richard B. Hochberg Yale University School of Medicine, New Haven, CT, USA 1. Krishnan V, et al. (2004) Mol Pharm doi: 10.1124/mol.104.005272. 2. Centrella M, et al. (2004) Mol Endocrinol 18:1120-1130. 3. Kousteni S, et al. (2002) Science 298:843-846. 4. Kousteni S, et al. (2003) J Clin Invest 111:1651-1664. 5. Penning TM (2003) Hum Reprod Update 9:193-205. 6. Napoli JL (2001) Mol Cell Endocrinol 171:103-109.
Author's Response 1 December 2004
Gary Krishnan, Corresponding Author Lilly Research Laboratories Send letter to journal: Re: Author's Response krishnan_Gary{at}lilly.com Gary Krishnan	The authors wish to indicate that upon the request of the reviewers, we evaluated the levels of the 3a-HSD gene product in the 2 cell lines (LA-20, and LnCAP) we believe reflect the genotropic effect of estren. However, using up to 35 cycles of PCR, we were unable to detect the gene product for 3a-HSD. In contrast, liver mRNA, used as positive control, showed the appropriately amplified product after 20-25 cycles of PCR. In addition, the authors have clearly stated (last paragraph of discussion) "in addition to the conversion to 19-nortestosterone in certain cells, estren has a direct genotropic action via AR". This statement is consistent with the fundamental similarity in the take home message made by these 2 independent studies, namely, the potential risk for genotropic action mediated by AR, when estren is used in a clinical setting. Gary Krishnan Lilly Research Laboratories Indianapolis, IN