Homologous and heterologous β-adrenergic desensitization in hepatocytes. Additivity and effect of pertussis toxin

S. M Teresa Hernández-Sotomayor, Marina Macías-Silva, Magdalena Plebañski, J. Adolfo García-Sáinz

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Abstract

In hepatocytes obtained from hypothyroid rats, phorbol myristate acetate (PMA) and vasopressin diminished the accumulation of cyclic AMP and the stimulation of ureagenesis induced by isoprenaline or glucagon without altering significantly the accumulation of cyclic AMP induced by forskolin. Pretreatment with PMA markedly reduced the stimulation of ureagenesis and the accumulation of cyclic AMP induced by isoprenaline or glucagon. In membranes from cells pretreated with PMA, the stimulation of adenylate cyclase induced by isoprenaline + GTP, glucagon + GTP or by Gpp[NH]p were clearly diminished as compared to the control, whereas forskolin-stimulated activity was not affected. The data indicate heterologous desensitization of adenylate cyclase. It was also observed that the homologous (García-Sáinz J.A. and Michel, B. (1987) Biochem. J. 246, 331-336) and this heterologous β-adrenergic desensitizations were additive. Pertussis toxin treatment markedly reduced the heterologous desensitization of adenylate cyclase but not the homologous β-adrenergic desensitization. It is concluded that the homologous and heterologous desensitizations involve different mechanisms. The homologous desensitization seems to occur at the receptor level, whereas the heterologous probably involves the guanine nucleotide-binding regulatory protein, Ns.

Original languageEnglish
Pages (from-to)311-319
Number of pages9
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Volume972
Issue number3
DOIs
Publication statusPublished - 9 Dec 1988
Externally publishedYes

Keywords

  • Adenylate cyclase
  • Homologous-heterologous desensitization
  • Pertussis toxin
  • Phorbol esters
  • Protein kinase C
  • β-Adrenoceptor

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