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首页> 外文期刊>Developmental genetics >Sequential up‐regulation of thyroid hormone β receptor, ornithine transcarbamylase, and carbamyl phosphate synthetase mRNAs in the liver ofRana catesbeianatadpoles during spontaneous and thyroid hormone‐induced metamorphosis
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Sequential up‐regulation of thyroid hormone β receptor, ornithine transcarbamylase, and carbamyl phosphate synthetase mRNAs in the liver ofRana catesbeianatadpoles during spontaneous and thyroid hormone‐induced metamorphosis

机译：Sequential up‐regulation of thyroid hormone β receptor, ornithine transcarbamylase, and carbamyl phosphate synthetase mRNAs in the liver ofRana catesbeianatadpoles during spontaneous and thyroid hormone‐induced metamorphosis

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AbstractDuring both spontaneous and thyroid hormone (TH)‐induced metamorphosis, theRana catesbeianatadpole undergoes postembryonic developmental changes in its liver which are necessary for its transition from an ammonotelic larva to a ureotelic adult. Although this transition ultimately results from marked increases in the activities and/or de novo synthesis of the urea cycle enzymes, the precise molecular means by which TH exerts this tissue‐specific response are presently unknown. Recent reports, using RNA from wholeXenopus laevistadpole homogenates and indirect means of measuring TH receptor (TR) mRNAs, suggest a correlation between the up‐regulation of TRβ‐mRNAs and the general morphological changes occurring during amphibian metamorphosis. To assess whether or not this same relationship exists in a TH‐responsive tissue, such as liver, we isolated and characterized a cDNA clone containing the complete nucleotide sequence for aR. catesbeianaurea cycle enzyme, ornithine transcarbamylase (OTC), as well as a genomic clone containing a portion of the hormone‐binding domain of aR. catesbeianaTRβ gene. Through use of these homologous sequences and a heterologous cDNA fragment encoding rat carbamyl phosphate synthetase (CPS), we directly determined the relative levels of the TRβ, OTC, and CPS mRNAs in liver from spontaneous and TH‐induced tadpoles. Our results establish that TH affects an up‐regulation of mRNAs for its own receptor prior to up‐regulating CPS and OTC mRNAs. Moreover, results with cultured tadpole liver demonstrate that TH, in the absence of any other hormonal influence, can affect an up‐regulation of both the TRβ and OTC mRNAs.

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