Renal Sodium Excretion Consequent to Pharmacogenetic Activation of Gq-DREADD in Principal Cells.

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 versus 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 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 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 affect ENaC and renal sodium excretion. These studies represent the first use of the pharmacogenetics DREADD technology in the renal tubule; and demonstrate that selective activation of the P2Y2 receptor and Gq signaling in principal cells is sufficient to promote renal salt excretion.