Abstract
Administration of dihydrotestosterone to estrogen-stimulated chicks induces a synergistic increase in ovomucoid mRNA synthesis and accumulation in the oviduct without affecting the synthesis of ovalbumin mRNA. This synergism is accompanied by an increase in nuclear estrogen receptors which could not be produced by simply increasing the maintenance dose of estrogen. Synergistic interactions between estrogen and dihydrotestosterone are also observed when they are added to oviduct explants in vitro. In addition to these synergistic effects, dihydrotestosterone is capable of maintaining the synthesis of ovalbumin and ovomucoid mRNAs after estrogen withdrawal in vivo. Analysis of total biologically active estrogen in the serum indicates that dihydrotestosterone does not interfere with estrogen elimination. Dihydrotestosterone also reinduces ovalbumin and ovomucoid gene transcription when injected into birds withdrawn from estrogen for less than 5 days; however, after several weeks of estrogen withdrawal, dihydrotestosterone is ineffective. Dihydrotestosterone alone acts directly on cultured oviduct explants to restimulate transcription of the ovalbumin and ovomucoid genes. Moreover, dihydrotestosterone effectively induces ovalbumin mRNA in the presence of the anti-estrogen, tamoxifen. These results indicate that androgen receptors can act either in concert with or independently of estrogen receptors to mediate specific gene transcription.
Highlights
Administration of dihydrotestosterone to estrogen- thesis is unaffected [6,9].Recent observations on thleevels of stimulated chicks induces asynergistic increase in ovo- androgen receptors in the presence and absence of estrogen mucoid mRNA synthesis and accumulationin the ovi- suggest thatestrogenis responsible fortheinductionand ductwithout affecting the synthesis ofovalbumin maintenance of cytosolic androgenreceptors in the chick mRNA
Polysomal RNA by oligo(dT) cellulose chromatography and sucrose gradients yielded an enrichedmRNA, fraction; ['HIcDNA was synthesized from this mRNA [12] and characterized by hybridization to hen polysomal RNA, pOV DNA, and pMU DNA.The results shown in Fig. 1A indicated that the cDNA was heavily contaminated with
TranscriptionalRegulation of the OvomucoidGene by Dihydrotestosterone-We have shown previously that dihydrotestosterone acts synergistically with estrogens to stimulate total RNA and protein synthesi(s6).The synthetic rates of most of the egg white proteins are enhanced coordinantly, such that the relative rates of synthesis remain the same; the relative rate of ovomucoid synthesis increases-2-fold [6].To investigate the preferential stimulation of ovomucoid synthesis by dihydrotestosterone, we prepared specific cDNA probes forovomucoid (Fig. 1) and ovalbumintoquantitatetheamount of their espective mRNAs
Summary
After 1 h at 37 "C, the reaction was adjusted to 1%sodium dodecyl sulfate, 5mM EDTA, and 25 pg/ml of proteinase K and incubated at 45 "C for 30 min. The purified RNA prepared from pMU DNA was hybridized to the[3H]cDNA in 100 pl of 0.3 M NaC1, 10 mM Tris (pH7.5), 2 mM EDTA, and 0.15% sodium dodecyl sulfate at 68 "C for 16 h. The mixture was incubated for 5 min with DNase I at 10pg/ml; sodium dodecyl sulfate was added to 18and themixture was digested with 100 pg/ml of proteinase K, followed by phenol/chloroform extraction. 7.5), 5 mM MgCL, 1 mM CaC12,1mM MnCI2for 30 min at 37 "C.The RNA was eluted from the fiters by adjusting the reaction to 1% sodium dodecyl sulfate and 10 mM EDTA and incubating at 68 "C for. Serum estrogen is described in terms of estradiol equivalents, based on its ability to compete with 17p['Hlestradiol for the estrogen receptor
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