Endocrine Abstracts

Several studies demonstrated that the thyroid hormones (TH) downregulate the transcriptional rate of beta and alpha TSH subunits. Recent data showed that T₃ also acts posttranscriptionally reducing the polyadenylation and translational rate of the beta TSH mRNA, when acutely administered to thyroidectomized (Tx) rats. This study aimed to investigate whether similar effects occur for the alpha subunit synthesis after acute administration of T₃ or T₄, which would also influence the synthesis of LH and FSH. For this, euthyroid (sham-operated, SO) and Tx rats were treated with physiological or supraphysiological doses of T₃, T₄ or saline, and killed by decapitation, 30 min thereafter. Some Tx rats were also subjected to T₃ treatment with supraphysiological dose for 5 days. The pituitaries were removed for evaluation of the fraction of alpha subunit mRNA associated with ribosomes, the total mRNA content and its degree of polyadenylation and the total protein content by RT/qPCR, RACE-PAT assay and western blotting, respectively. It was shown in Tx group an increased alpha mRNA content, without alterations on the polyadenylation degree, and reduced protein content compared with SO group. T₃ administration for 30 min or 5 days reduced the content of mRNA associated with ribosomes, and increased the total protein content; T₄ treatment for 30 min decreased the total mRNA content, and increased the poly(A) tail length and the total protein content in pituitary. Thus, both T₃ and T₄ rapidly regulate the posttranscriptional steps of alpha subunit synthesis modifying the content, stability and translational rate of its mRNA, as well as its secretion, which might affect TSH, FSH and LH economy.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.