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      Dopamine D2-like receptors are expressed in pancreatic beta cells and mediate inhibition of insulin secretion.

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          Abstract

          Dopamine signaling is mediated by five cloned receptors, grouped into D1-like (D1 and D5) and D2-like (D2, D3 and D4) families. We identified by reverse transcription-PCR the presence of dopamine receptors from both families in INS-1E insulin-secreting cells as well as in rodent and human isolated islets. D2 receptor expression was confirmed by immunodetection revealing localization on insulin secretory granules of INS-1E and primary rodent and human beta cells. We then tested potential effects mediated by the identified receptors on beta cell function. Dopamine (10 microM) and the D2-like receptor agonist quinpirole (5 microM) inhibited glucose-stimulated insulin secretion tested in several models, i.e. INS-1E beta cells, fluorescence-activated cell-sorted primary rat beta cells, and pancreatic islets of rat, mouse, and human origin. Insulin exocytosis is controlled by metabolism coupled to cytosolic calcium changes. Measurements of glucose-induced mitochondrial hyperpolarization and ATP generation showed that dopamine and D2-like agonists did not inhibit glucose metabolism. On the other hand, dopamine decreased cell membrane depolarization as well as cytosolic calcium increases evoked by glucose stimulation in INS-1E beta cells. These results show for the first time that dopamine receptors are expressed in pancreatic beta cells. Dopamine inhibited glucose-stimulated insulin secretion, an effect that could be ascribed to D2-like receptors. Regarding the molecular mechanisms implicated in dopamine-mediated inhibition of insulin release, our results point to distal steps in metabolism-secretion coupling. Thus, the role played by dopamine in glucose homeostasis might involve dopamine receptors, expressed in pancreatic beta cells, modulating insulin release.

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          Author and article information

          Journal
          J Biol Chem
          The Journal of biological chemistry
          American Society for Biochemistry & Molecular Biology (ASBMB)
          0021-9258
          0021-9258
          Nov 04 2005
          : 280
          : 44
          Affiliations
          [1 ] Department of Cell Physiology and Metabolism, University Medical Center, Geneva University Hospitals, CH-1211 Geneva 4, Switzerland. rubiweiss@yahoo.com
          Article
          S0021-9258(20)59318-6
          10.1074/jbc.M505560200
          16129680
          a969de06-4e8d-4253-85ad-316e1e8f8d00
          History

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