PHARMACOLOGICAL CHARACTERIZATION AND AUTORADIOGRAPHIC LOCALIZATION OFA PUTATIVE DOPAMINE D-3 RECEPTOR IN THE RAT-KIDNEY

The pharmacological profile and the microanatomical localisation of a putative dopamine D-3 receptor in the rat renal cortex were investigat ed using radioligand binding assay and light microscope autoradiograph y techniques. [H-3]7-hydroxy-N,N-di-n-propyl-2-amino-tetraline ([H-3]7 -OH-DPAT) was used as a ligand. [H-3]7-OH-DPAT was bound specifically to sections of renal cortex. The binding was time-, temperature- and c oncentration-dependent, of high affinity and guanine nucleotide-insens itive. The dissociation constant (K-d) value was 0.57 +/- 0.02 nM and the maximum density of binding sites (B-max) was 62.4 +/- 3.5 fmol/mg tissue. The pharmacological profile of [H-3]7-OH-DPAT binding to secti ons of rat renal cortex suggests the labelling of a dopamine D-3 recep tor. Light microscope autoradiography revealed the accumulation of the radioligand primarily within cortical tubules and to a lesser extent in the glomerular tuft. In glomeruli, binding sites were found mainly in mesangium and mesangial cells. The demonstration of a putative dopa mine D-3 receptor in slide-mounted sections of rat renal cortex sugges ts that appropriate radioligand binding assay techniques combined with autoradiography, may contribute to characterise peripheral dopamine r eceptor subtypes. (C) 1997 Elsevier Science B.V.