title: The endocannabinoid system in renal cells: regulation of Na(+) transport by CB1 receptors through distinct cell signalling pathways.
abstract: OBJECTIVE
  The function of the endocannabinoid system (ECS) in renal tissue is not completely understood. Kidney function is closely related to ion reabsorption in the proximal tubule, the nephron segment responsible for the re-absorption of 70-80% of the filtrate. We studied the effect of compounds modulating the activity of cannabinoid (CB) receptors on the active re-absorption of Na(+) in LLC-PK1 cells.
  
  
  METHODS
  Changes in Na(+) /K(+) -ATPase activity were assessed after treatment with WIN55,212-2 (WIN), a non-selective lipid agonist, and haemopressin (HP), an inverse peptide agonist at CB1 receptors. Pharmacological tools were used to investigate the signalling pathways involved in the modulation of Na(+) transport.
  
  
  RESULTS
  In addition to CB1 and CB2 receptors and TRPV1 channels, the mRNAs encoding for enzymes of the ECS were also expressed in LLC-PK1. WIN (10(-7)  M) and HP (10(-6)  M) altered Na(+) re-absorption in LLC-PK1 in a dual manner. They both acutely (after 1 min) increased Na(+) /K(+) -ATPase activity in a TRPV1 antagonist-sensitive way. WIN's stimulating effect persisted for 30 min, and this effect was partially blocked by a CB1 antagonist or a PKC inhibitor. In contrast, HP inhibited Na(+) /K(+) -ATPase after 30 min incubation, and this effect was attenuated by a CB1 antagonist or a PKA inhibitor.
  
  
  CONCLUSIONS
  The ECS is expressed in LLC-PK1 cells. Both CB1 receptors and TRPV1 channels regulate Na(+) /K(+) -ATPase activity in these cells, and are modulated by lipid and peptide CB1 receptor ligands, which act via different signalling pathways.
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.|Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Brazil.|CAPES Foundation, Ministry of Education of Brasil, Brasilia, Brazil.
authors.forename: L S
authors.initials: LS
authors.lastname: Sampaio
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.|Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Taveira Da Silva
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.|Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Brazil.
authors.forename: D
authors.initials: D
authors.lastname: Lima
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.|Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Brazil.
authors.forename: C L C
authors.initials: CL
authors.lastname: Sampaio
authors.affiliation: Endocanabinnoid Research Group, Istituto di Chimica Biomolecolare, CNR, Pozzuoli, Italy.
authors.forename: F A
authors.initials: FA
authors.lastname: Iannotti
authors.affiliation: Endocanabinnoid Research Group, Istituto di Chimica Biomolecolare, CNR, Pozzuoli, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Mazzarella
authors.affiliation: Endocanabinnoid Research Group, Istituto di Chimica Biomolecolare, CNR, Pozzuoli, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Di Marzo
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.|Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Brazil.|CAPES Foundation, Ministry of Education of Brasil, Brasilia, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Vieyra
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.|Instituto Nacional de Ciência e Tecnologia em Neurociência Translacional, Brazil.
authors.forename: R A M
authors.initials: RA
authors.lastname: Reis
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.|Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Brazil.|CAPES Foundation, Ministry of Education of Brasil, Brasilia, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Einicker-Lamas
mesh_terms: D000818:Animals; D048588:Benzoxazines / Q000494:pharmacology; D001692:Biological Transport; D000242:Cyclic AMP / Q000378:metabolism; D063388:Endocannabinoids / Q000378:metabolism*; D006454:Hemoglobins / Q000494:pharmacology; D007668:Kidney / Q000378:metabolism*; D018374:LLC-PK1 Cells; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043885:Receptor, Cannabinoid, CB2 / Q000378:metabolism; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013552:Swine; D050916:TRPV Cation Channels / Q000378:metabolism
chemical_list: D048588:Benzoxazines; D063388:Endocannabinoids; D006454:Hemoglobins; D009025:Morpholines; D009281:Naphthalenes; D010446:Peptide Fragments; D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D050916:TRPV Cation Channels; C473218:hemopressin; C103505:AM 251; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D012964:Sodium; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase