Cannabinoid Receptor Type 1 Activation Causes a Water Diuresis by Inducing an Acute Central Diabetes Insipidus in Mice.

Cannabis and synthetic cannabinoid consumption is increasing worldwide. Cannabis contains numerous phytocannabinoids that act on the G-protein-coupled cannabinoid receptors type 1 (CB1R) and type 2 (CB2R) expressed throughout the body, including the kidney. Essentially every organ, including the kidney, produces endocannabinoids (ECs), endogenous ligands to these receptors. Cannabinoids acutely increase urine output in rodents and humans, thus potentially influencing total-body water and electrolyte homeostasis. As the kidney collecting duct (CD) regulates total body water, acid/base, and electrolyte balance through specific functions of principal cells (PCs) and intercalated cells (ICs), we examined the cell-specific immunolocalization of CB1R in the mouse CD. Antibodies against either the C-terminus or N-terminus of CB1R consistently labeled AQP2(-) cells in the cortical and medullary CD, and thus presumably ICs. Given the well-established role of ICs in urinary acidification, we utilized a clearance approach in mice that were acid-loaded with 280 mM NH4Cl for 7d and non-acid-loaded mice treated with the cannabinoid receptor agonist, WIN55,212-2 (WIN), or a vehicle control. While WIN had no effect on urinary acidification, these WIN-treated mice had less apical+subapical AQP2 expression in PCs compared to controls and developed an acute diabetes insipidus (DI) associated with the excretion of large volumes of dilute urine. Mice maximally concentrated their urine when WIN + 1-desamino-8-d-arginine-vasopressin (desmopressin, DDAVP) were co-administered, consistent with central rather than nephrogenic DI. Although ICs express CB1R, the physiologic role of CB1R in this cell type remains to be determined.