Characterization, expression, and hormonal control of a thymic β2- adrenergic receptor

B. Marchetti, M. C. Morale, P. Paradis, M. Bouvier

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In the present study, we have characterized the β2-adrenergic receptor (β2-AR)-adenosine 3',5'-cyclic monophosphate (cAMP) system of the rat thymus gland and examined the hormonal regulation of the thymic β2-AR gene expression under physiological or pharmacological conditions accompanied by marked alterations of the sex steroid hormone milieu. We report here that membrane preparations of female rat thymic tissue contain iodocyanopindolol binding sites that exhibit pharmacological properties typical of a β-AR. Detailed analysis by computer modeling of the binding potencies of a large series of β1- and β2-adrenergic agonists and antagonists revealed predominantly the β2-AR subtype (78%) in rat thymus. This inference from radioligand binding studies was corroborated functionally by the rank order of potencies of a series of adrenergic agonists to stimulate the production of cAMP. Northern blot analysis, using a human β2-AR cDNA as a probe, revealed the presence of a mRNA of 2.3 kb, which is consistent with the size of the β2-AR mRNA found in other rat tissues. Physiological regulation of specific β2-AR in the rat thymus was indicated by significant increases in both receptor concentration and steady-state levels of β2-AR mRNA during the diestrous 2 and proestrous phases of the rat estrous cycle and pregnancy, whereas castration sharply reduced β2-AR numbers and transcript levels within the thymus. The modulation of the thymic β2-AR-cAMP signaling system by the preexisting sex steroid milieu, coupled with the sex-dependent adrenergic modulation of thymic cell-mediated immune response, may contribute to the various sex-related alterations in immune responsiveness and could play a role in sexually related immune disorders.

Original languageEnglish
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number5 30-5
Publication statusPublished - 1994


  • β/β-adrenergic receptor subtypes
  • adenylyl cyclase-adenosine 3',5'-cyclic monophosphate system
  • cell-mediated immune response
  • functional coupling
  • guanosine 5'-triphosphate
  • messenger ribonucleic acid concentration
  • sex dimorphism
  • sex steroids
  • thymocyte proliferation

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Physiology


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