The metamorphosis of Rhinella arenarum was induced precociously for 5 days, then blocked for 3 months to evaluate the role of thyroid hormones as modulators of morphoregulatory molecules such as E-cadherin, and β- and α-catenin during epithelium remodeling. We then performed an immunohistochemical and morphometric study of these molecules in the larval stomach. We show that 3,5,3'-triiodothyronine exerts a positive regulatory effect on E-cadherin and β- and α-catenin expression in stomach epithelium. This suggests continuous synthesis of E-cadherin, and β- and α-catenin; synthesis essentially is thyroid hormone-independent during premetamorphosis and early prometamorphosis, but it becomes thyroid hormone-dependent during metamorphic climax.

Cell adhesion molecules act as signal transducers from the extracellular environment to the cytoskeleton and the nucleus and consequently induce changes in the expression pattern of structural proteins. In this study, we showed the effect of thyroid hormone (TH) inhibition and arrest of metamorphosis on the expression of E-cadherin, -and -catenin in the developing kidney of Bufo arenarum. Cell adhesion molecules have selective temporal and spatial expression during development suggesting a specific role in nephrogenesis. In order to study mechanisms controlling the expression of adhesion molecules during renal development, we blocked the B. arenarum metamorphosis with a goitrogenic substance that blocks TH synthesis. E-cadherin expression in the proximal tubules is independent of thyroid control. However, the blockage of TH synthesis causes up-regulation of E-cadherin in the collecting ducts, the distal tubules and the glomeruli. The expression of -and -catenin in the collecting ducts, the distal tubules, the glomeruli and the mesonephric mesenchyme is independent of TH. TH blockage causes up-regulation of -and -catenin in the proximal tubules. In contrast to E-cadherin, the expression of the desmosomal cadherin desmoglein 1 (Dsg-1) is absent in the control of the larvae kidney during metamorphosis and is expressed in some interstitial cells in the KClO 4 treated larvae. According to this work, the Dsg-1 expression is down-regulated by TH. We demonstrated that the expression of E-cadherin, Dsg-1, -catenin and -catenin are differentially affected by TH levels, suggesting a hormone-dependent role of these proteins in the B. arenarum renal metamorphosis.Keywords: catenins, cadherins, metamorphosis, amphibians. Expressão das moléculas de adesão celular no desenvolvimento normale com a inibição do hormônio tireoidea do rim nas larvas do Bufo arenarum (Amphibia, Anura, Bufonidae) ResumoMoléculas de adesão celular atuam como tradutores do ambiente extracelular para o citoesqueleto e o núcleo e, conseqüentemente, induzindo mudanças no padrão da expressão das proteínas estruturais. Neste estudo, observamos os efeitos da inibição do hormônio tireóidea (TH) e detenção da metamorfose na expressão da E-caderina, -e -catenina no desenvolvimento do rim do Bufo arenarum. As moléculas de adesão celular durante o desenvolvimento têm uma expressão temporal e espacial seletiva, sugerindo um papel específico na nefrogênese. Com o propósito de estudar os mecanismos de controle da expressão das moléculas de adesão durante o desenvolvimento renal, bloqueou-se a metamorfose do B. arenarum com uma substancia goitrogênica que bloqueia a síntese de TH. A expressão da E-caderina nos tubos proximais é independente do controle da tireóide. Entretanto, o bloqueio da síntese de TH provoca uma sobre elevação da E-caderina nos dutos coletores, nos tubos distais e nos glomérulos. A expressão da -e -catenina nos dutos coletores, nos tubos distais, nos glomérulos e no mesênquima mesonéfrico é independente da TH. O bloqueio da TH causa uma so...

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Since the middle of last century there have been a plethora of studies trying to comprehend the fine control of adhesive contacts involved in establishment, maintainance and remodeling of epithelial architecture during animal development and adulthood. Depending on the experimental model, surprising and even contradictory data have been obtained. Among these, the in vivo systems outperform in vitro models in terms of understanding the animal biology.It is known that thyroid hormones (THs) modulate energy metabolism, growth and development by independent mechanisms. Thyroid calorigenesis is influenced predominantly via thyroid hormone receptors (TRs) that mediate synthesis of mitochondrial respiratory complexes and cell membrane sodium-potassium ATPase; whereas it is debate matter if many of the TH effects over epithelial development are principally mediated via growth factors, TRs or transmembrane proteins.Present work presents molecular evidences that T3 modulates the epithelial adhesive potential during gut remodeling in X. laevis development, differentially activating E-cadherin, β-catenin and α-catenin genes, and downstream, modulating small GTP-binding proteins involved in adhesive epithelial properties.