Stimulation of Gq‐coupled metabotropic P2Y2 receptors decrease the activity of ENaC in renal principal cells of the distal nephron. The physiological consequences of disrupting P2Y2 receptor signaling in the P2Y2 receptor knockout mouse are decreased sodium excretion and increased arterial blood pressure. However, because of the global nature of this knockout model, the quantitative contribution of ENaC and the distal nephron verses that of upstream renal vascular and tubular elements to changes in urinary excretion and arterial blood pressure are obscure. Moreover, it is uncertain whether stimulation of P2Y2 receptor inhibition of ENaC is sufficient alone to drive renal sodium excretion. Here we test the sufficiency of targeted stimulation of Gq signaling in principal cells of the distal nephron and P2Y2 receptors to increase renal sodium excretion using a pharmacogenetic approach and selective agonism of the P2Y2 receptor. Selective stimulation of the P2Y2 receptor with the ligand, MRS2768, decreased ENaC activity in freshly isolated tubules as assessed with patch clamp electrophysiology; and rapidly increased urinary sodium excretion as assessed in metabolic cages. Similarly, selective agonism with clozapine N‐oxide (CNO) of hM3Dq‐DREADD restrictively expressed in principal cells of the distal nephron decreased ENaC activity with consequent increases in sodium excretion. CNO when applied to control littermates failed to impact ENaC and renal sodium excretion. These studies represent the first use of the pharmacogenetics DREADD technology in the kidney; and demonstrate that selective activation of the P2Y2 receptor and Gq signaling in principal cells is sufficient to promote renal salt excretion.
Support or Funding Information
This research was supported by NIH/NIDDK grants R01DK98460, R01DK103758 and American Heart Association grant 17GRNT32920002 to JDS
This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
The Epithelial Na+ Channel, ENaC, is the final arbiter of sodium excretion in the kidneys. As such, discretionary control of ENaC by hormones is critical to the fine‐tuning of electrolyte and water excretion and consequently, blood pressure. Local paracrine purinergic signaling intrinsic to the distal nephron inhibits ENaC activity via Gq‐coupled apical P2Y2 receptors. This purinergic signaling system functions in parallel with the renin‐AngII‐aldosterone system to maintain blood pressure. Loss of purinergic inhibition of ENaC causes salt‐sensitivity and elevated blood pressure. To further elaborate the cellular mechanisms and physiological consequences of local purinergic regulation of ENaC and to test whether stimulation of this inhibitory regulation of ENaC could ameliorate forced salt‐sensitivity in the DOCA‐salt mouse, we created an excitatory hM3Dq DREADD mouse with conditional expression of this synthetic receptor in principal cells. Activation of this DREADD receptor in these mice promoted renal Na+ excretion even under conditions, such as a Na+ free feeding regimen, that favored renal Na+ conservation. On‐going experiments test if this facilitation of Na+ excretion protects principal cell‐specific hM3Dq DREADD mice from elevations in blood pressure resulting from DOCA‐salt treatment.Support or Funding InformationThis research was supported by American Heart Association grants 15GRNT22930030 & 17GRNT3292002 (to JDS), and F32DK104572 (to EM).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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