title: Anandamide inhibits transport-related oxygen consumption in the loop of Henle by activating CB1 receptors.
abstract: The energy required for active Na chloride reabsorption in the thick ascending limb (TAL) depends on oxygen consumption and oxidative phosphorylation (OXP). In other cells, Na transport is inhibited by the endogenous cannabinoid anandamide through the activation of the cannabinoid receptors (CB) type 1 and 2. However, it is unclear whether anandamide alters TAL transport and the mechanisms that could be involved. We hypothesized that anandamide inhibits TAL transport via activation of CB1 receptors and NO. For this, we measured oxygen consumption (Q(O(2))) in TAL suspensions to monitor the anandamide effects on transport and OXP. Anandamide reduced Q(O(2)) in a concentration-dependent manner. During Na-K-2Cl cotransport and Na/H exchange inhibition, anandamide did not inhibit TAL Q(O(2)). To test the role of the cannabinoid receptors, we used specific agonists and antagonists of CB1 and CB2 receptors. The CB1-selective agonist WIN55212-2 reduced Q(O(2)) in a concentration-dependent manner. Also, the CB1 receptor antagonist rimonabant blocked the effect of anandamide on Q(O(2)). In contrast, the CB2-selective agonist JHW-133 had no effect on Q(O(2)), while the CB2 receptor antagonist AM-630 failed to block the anandamide effects on Q(O(2)). To confirm these results, we measured CB1 and CB2 receptor expression and only CB1 expression was detected. Because CB1 receptors are strong nitric oxide synthase (NOS) stimulators and NO inhibits transport in TALs, we evaluated the role of NO. Anandamide stimulated NO production and the NOS inhibitor N(G)-nitro-L-arginine methyl ester blocked the anandamide effects on Q(O(2)). We conclude that anandamide inhibits TAL Na transport-related Q(O(2)) via activation of CB1 receptor and NOS.
authors.affiliation: School of Chemistry Science, Catholic Univ. of Córdoba, Consejo Nacional de Investigaciones Científicas y Técnicas, Córdoba, Argentina. guillermo.silva@jrobertcade.org.ar
authors.forename: Guillermo B
authors.initials: GB
authors.lastname: Silva
authors.forename: Douglas K
authors.initials: DK
authors.lastname: Atchison
authors.forename: Luis I
authors.initials: LI
authors.lastname: Juncos
authors.forename: Néstor H
authors.initials: NH
authors.lastname: García
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D048588:Benzoxazines / Q000494:pharmacology; D063386:Cannabinoid Receptor Agonists / Q000494:pharmacology*; D063387:Cannabinoid Receptor Antagonists / Q000494:pharmacology; D002186:Cannabinoids / Q000494:pharmacology; D018929:Cell Culture Techniques; D063388:Endocannabinoids / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D008138:Loop of Henle / Q000187:drug effects*; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010101:Oxygen Consumption / Q000187:drug effects*; D010880:Piperidines / Q000494:pharmacology; D053284:Polyunsaturated Alkamides / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists* / Q000037:antagonists & inhibitors; D000077285:Rimonabant
chemical_list: D001095:Arachidonic Acids; D048588:Benzoxazines; D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; D002186:Cannabinoids; D063388:Endocannabinoids; D007211:Indoles; D009025:Morpholines; D009281:Naphthalenes; D010880:Piperidines; D053284:Polyunsaturated Alkamides; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D009569:Nitric Oxide; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D019001:Nitric Oxide Synthase; D000077285:Rimonabant; C432747:1,1-dimethylbutyl-1-deoxy-Delta(9)-THC; C094023:iodopravadoline; C078814:anandamide; D019331:NG-Nitroarginine Methyl Ester