title: Intracellular signalling pathways in the vasoconstrictor response of mouse afferent arterioles to adenosine.
abstract: OBJECTIVE
  Adenosine causes vasoconstriction of afferent arterioles of the mouse kidney through activation of adenosine A(1) receptors and Gi-mediated stimulation of phospholipase C. In the present study, we further explored the signalling pathways by which adenosine causes arteriolar vasoconstriction.
  
  
  RESULTS
  Adenosine (10(-7) M) significantly increased the intracellular calcium concentration in mouse isolated afferent arterioles measured by fura-2 fluorescence. Pre-treatment with thapsigargin (2 microM) blocked the vasoconstrictor action of adenosine (10(-7) M) indicating that release of calcium from the sarcoplasmic reticulum (SR), stimulated presumably by IP(3), is involved in the adenosine contraction mechanism of the afferent arteriole. In agreement with this notion is the observation that 2 aminoethoxydiphenyl borate (100 microM) blocked the adenosine-induced constriction whereas the protein kinase C inhibitor calphostin C had no effect. The calcium-activated chloride channel inhibitor IAA-94 (30 microM) inhibited the adenosine-mediated constriction. Patch clamp experiments showed that adenosine treatment induced a depolarizing current in preglomerular smooth muscle cells which was abolished by IAA-94. Furthermore, the vasoconstriction caused by adenosine was significantly inhibited by 5 microM nifedipine (control 8.3 +/- 0.2 microM, ado 3.6 +/- 0.6 microM, ado + nifedipine 6.8 +/- 0.2 microM) suggesting involvement of voltage-dependent calcium channels.
  
  
  CONCLUSIONS
  We conclude that adenosine mediates vasoconstriction of afferent arterioles through an increase in intracellular calcium concentration resulting from release of calcium from the SR followed by activation of Ca(2+)-activated chloride channels leading to depolarization and influx of calcium through voltage-dependent calcium channels.
authors.affiliation: National Institute of Diabetes, and Digestive and Kidney Diseases, NIH, Bethesda, MD, USA. pbhansen@health.sdu.dk
authors.forename: P B
authors.initials: PB
authors.lastname: Hansen
authors.forename: U G
authors.initials: UG
authors.lastname: Friis
authors.forename: T R
authors.initials: TR
authors.lastname: Uhrenholt
authors.forename: J
authors.initials: J
authors.lastname: Briggs
authors.forename: J
authors.initials: J
authors.lastname: Schnermann
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000344:Afferent Pathways / Q000187:drug effects*; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001160:Arterioles; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D004730:Endothelium, Vascular / Q000187:drug effects*; D005260:Female; D006016:Glycolates / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors; D007424:Intracellular Fluid / Q000737:chemistry / Q000378:metabolism; D007678:Kidney Glomerulus / Q000098:blood supply; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009281:Naphthalenes / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010477:Perfusion; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D013268:Stimulation, Chemical; D019284:Thapsigargin / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors
chemical_list: D000577:Amides; D001896:Boron Compounds; D002121:Calcium Channel Blockers; D018118:Chloride Channels; D006016:Glycolates; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009281:Naphthalenes; D011725:Pyridines; D014662:Vasoconstrictor Agents; C061465:calphostin complex; C108830:Y 27632; C027513:N(6)-cyclohexyladenosine; C015765:MK 473; D019284:Thapsigargin; C109986:2-aminoethoxydiphenyl borate; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D009543:Nifedipine; D000241:Adenosine; D002118:Calcium