Pharmacological characterisation and autoradiographic localisation of a putative dopamine D 3 receptor in the rat kidney

Abstract

The pharmacological profile and the microanatomical localisation of a putative dopamine D 3 receptor in the rat renal cortex were investigated using radioligand binding assay and light microscope autoradiography techniques. [ 3 H ]7-hydroxy- N, N-di- n-propyl-2-aminotetraline ([ 3 H ]7-OH-DPAT) was used as a ligand. [ 3 H ]7-OH-DPAT was bound specifically to sections of renal cortex. The binding was time-, temperature-, concentration-dependent, of high affinity and guanine nucleotide-insensitive. 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 [ 3 H ]-7-OH-DPAT binding to sections of rat renal cortex suggests the labelling of a dopamine D 3 receptor. 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 dopamine D 3 receptor in slide-mounted sections of rat renal cortex suggests that appropriate radioligand binding assay techniques combined with autoradiography, may contribute to characterise peripheral dopamine receptor subtypes.