RT Journal Article SR Electronic T1 Mechanism of diuresis and natriuresis by cannabinoids: evidence for inhibition of Na+,K+-ATPase in mouse kidney thick ascending limb tubules JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP JPET-AR-2020-000163 DO 10.1124/jpet.120.000163 A1 Joseph K. Ritter A1 Ashfaq Ahmad A1 Shoba Mummalaneni A1 Zdravka Daneva A1 Sara K. Dempsey A1 Ningjun Li A1 Pin-Lan Li A1 Vijay Lyall YR 2020 UL http://jpet.aspetjournals.org/content/early/2020/10/21/jpet.120.000163.abstract AB The endocannabinoid, anandamide (AEA), stimulates cannabinoid receptors (CBR) and is enriched in the kidney, especially the renal medulla. AEA infused into the renal outer medulla of mice stimulates urine flow rate and salt excretion. Here we show that these effects are blocked by the CBR Type I (CB1) inverse agonist, rimonabant. Immunohistochemical analysis demonstrated the presence of CB1 in thick ascending limb (TAL) tubules. Western immunoblotting demonstrated the presence of CB1 (52 KDa) in the cortex and outer medulla of mouse kidney. The effect of direct (CP55940 (CP) or AEA) or indirect (fatty acyl amide hydrolase (FAAH) inhibitor, PF3845 (PF)) cannabinoidimetics on Na+ transport in isolated mouse TAL tubules was studied using the Na+-sensitive dye, SBFI-AM. Switching from 0 Na+ solution to control Ringers solution (CR) rapidly increased TAL cell [Na+]i. Addition of CP to CR produced a further elevation, similar in magnitude to that of ouabain, a Na+-K+-ATPase inhibitor. This [Na+]i-elevating effect of CP was time-dependent, required the presence of Na+ in the bathing solution, and was insensitive to Na+-K+-2Cl- co-transporter (NKCC2) inhibition. Addition of PF to CR elevated [Na+]i in FAAH wildtype but not FAAH knockout (KO) TALs, whereas the additions of CP and AEA to PF-treated FAAH KO TALs increased [Na+]i. An interaction between cannabinoidimetics and ouabain (Ou) was observed. Ou produced less increase in [Na+]i after cannabinoidimetic treatment, whereas cannabinoidimetics had less effect after Ou treatment. It is concluded that cannabinoidimetics, including CP and AEA, inhibit Na+ transport in TALs by inhibiting Na+ exit via Na+-K+-ATPase. Significance Statement Cannabinoids including endocannabinoids induce renal urine and salt excretion and are proposed to play a physiological role in the regulation of blood pressure. Our data suggest that the mechanism of the cannabinoids involves inhibition of the sodium pump, Na+,K+-ATPase, in thick ascending limb cells and, likely, other proximal and distal tubular segments of the kidney nephron.