Departments of Pharmacology and Toxicology (J.K.R., A.A., Z.D., S.K.D., N.L., P.-L.L.) and Physiology and Biophysics (S.M., V.L.), Virginia Commonwealth University, Richmond, Virginia
Departments of Pharmacology and Toxicology (J.K.R., A.A., Z.D., S.K.D., N.L., P.-L.L.) and Physiology and Biophysics (S.M., V.L.), Virginia Commonwealth University, Richmond, Virginia.
J Pharmacol Exp Ther. 2021 Jan;376(1):1-11. doi: 10.1124/jpet.120.000163. Epub 2020 Oct 21.
The endocannabinoid, anandamide (AEA), stimulates cannabinoid receptors (CBRs) 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 1 (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 Ringer's solution (CR) rapidly increased TAL cell [Na] Addition of CP to CR produced a further elevation, similar in magnitude to that of ouabain, a Na-K-ATPase inhibitor. This [Na]-elevating effect of CP was time-dependent, required the presence of Na in the bathing solution, and was insensitive to Na-K-2Cl cotransporter inhibition. Addition of PF to CR elevated [Na] in FAAH wild-type but not FAAH knockout (KO) TALs, whereas the additions of CP and AEA to PF-treated FAAH KO TALs increased [Na] An interaction between cannabinoidimetics and ouabain (Ou) was observed. Ou produced less increase in [Na] 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.
内源性大麻素，花生四烯酸乙醇酰胺（AEA），刺激大麻素受体（CBRs），并在肾脏中富集，尤其是在肾髓质中。将 AEA 注入小鼠的肾外髓质会刺激尿流量和盐排泄。在这里，我们表明这些作用被 CBR 类型 1（CB1）反向激动剂利莫那班阻断。免疫组织化学分析表明 CB1 存在于厚升支（TAL）小管中。Western 免疫印迹显示 CB1（52 kDa）存在于小鼠肾脏的皮质和外髓质中。直接[CP55940（CP）或 AEA]或间接[脂肪酸酰胺水解酶（FAAH）抑制剂，PF3845（PF）]大麻素激动剂对分离的小鼠 TAL 管中 Na 转运的影响使用 Na 敏感染料 SBFI-AM 进行研究。从 0 Na 溶液切换到对照 Ringer's 溶液（CR）会迅速增加 TAL 细胞[Na]，向 CR 中加入 CP 会进一步升高，其幅度与 Na-K-ATP 酶抑制剂哇巴因相似。CP 的这种[Na]升高作用是时间依赖性的，需要在浴液中存在 Na，并且对 Na-K-2Cl 共转运体抑制不敏感。向 CR 中加入 PF 会升高 FAAH 野生型但不是 FAAH 敲除（KO）TAL 中的[Na]，而向 PF 处理的 FAAH KO TAL 中加入 CP 和 AEA 会增加[Na]。观察到大麻素激动剂和哇巴因（Ou）之间的相互作用。在大麻素激动剂处理后，哇巴因引起的[Na]增加减少，而在哇巴因处理后，大麻素激动剂的作用减少。结论是，包括 CP 和 AEA 在内的大麻素激动剂通过抑制 Na-K-ATP 酶的 Na 外排来抑制 TAL 中的 Na 转运。意义陈述：包括内源性大麻素在内的大麻素诱导肾脏尿液和盐排泄，并被提议在调节血压中发挥生理作用。我们的数据表明，大麻素的作用机制涉及抑制厚升支细胞中的钠泵，Na-K-ATP 酶，并且可能涉及肾脏肾单位的其他近端和远端肾小管段。
