Fisiologia dos adrenoceptores cardíacos

Autores/as

  • Wagner Jesus Pinto
  • Silvana Maria Guida-Cardoso
  • Miguel Arcanjo Areas

Palabras clave:

colesterol, fisiologia, fisiologia cardiovascular, receptores adrenérgicos

Resumen

Adrenoceptores (receptores adrenérgicos ou AR. 's) são proteínas de sete alças ancoradas à membrana plasmática, que respondem a estímulos catecolaminér­ gicos. São classificados em a-adrenoceptores e  -adrenoceptores, sendo que há dois subtipos principais de a receptores adrenérgicos (a e a2) e três subtipos de -adrenoceptores ( 1, 2 e ), embora se especule sobre a existência de um receptor 4. Os receptores adrenérgicos-a1 ativam a maquinaria da fosfolipase C, gerando inositol trifosfato (IP) e diacilglicerol como segundos mensageiros intracelulares, enquanto que os receptores adrenérgicos-a  estão acoplados à adenilato ciclase e, no meio intracelular, reduzem a formação de adenosina monofosfato cíclico, inibindo o canal de cálcio, de maneira que a ativação dessa subclasse de receptores promove efeitos inibitórios na célula onde está presente. Em  contrapartida, todos os receptores adrenérgicos aumentam a formação de adenosina monofosfato cíclico intracelular. Na vigência de estímulos prolongados, os receptores adrenérgicos sofrem dessensibilização, assim como vários outros sistemas biológicos de sinalização. A dessensibilização pode se dar pelos seguintes meios: fosforilação via cinases específicas; fosforilação por cinases efetoras; por endocitose do receptor; down-regu!ation, via fosforilação da subunidade a da proteína G; e, finalmente, por redução da transcrição intracelular de RNA-mensageiro. A integridade fisiológica dos receptores adrenérgicos é dependente de um meio ideal que pode sofrer alterações em função de diversos fatores, tais como a hipercolesterolemia e o estresse oxidativo.

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Citas

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Publicado

2005-02-28

Cómo citar

Pinto, W. J., Guida-Cardoso, S. M., & Areas, M. A. (2005). Fisiologia dos adrenoceptores cardíacos. Revista De Ciências Médicas, 14(1). Recuperado a partir de https://seer.sis.puc-campinas.edu.br/cienciasmedicas/article/view/1196

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