Autoradiographic localization and characterization of substance P binding in dog kidney

The autoradiographic localization of [¹²⁵I]Bolton-Hunter substance P (BHSP) was examined in slide-mounted sections of dog kidney and dog renal artery and vein. Biochemical characterization of the binding in sections of dog kidney, demonstrated that BHSP binds to a population of non-interacting sites with high affinity (K_D = 0.11 ± 0.02 nM, B_max = 0.29 ± 0.05 fmol/section). The binding was displaced by tachykinins in the order SP > NKA ≫ NKB, indicative of binding to NK-1 receptors. BHSP binding to dog kidney was localized over glomeruli and endothelium of intrarenal arteries. There was binding associated with the endothelium and adventitia of the renal artery but not the vein. Binding of BHSP to arcuate arteries and to the renal artery was dependent on the presence of an intact endothelium. No evidence was obtained for receptors associated with any renal tubules. These results suggest that in the dog, vasodilatation, diuresis and natriuresis in response to SP may result from an action primarily on the vascular elements of the kidney.