Dopamine D₂-like receptors in the rat kidney: Effect of denervation

The effects of monolateral denervation induced by renal artery occlusion on dopamine D₂-like receptors were assessed in rat kidney using radioligand binding assay and autoradiographic techniques. [³H]spiperone was used as a ligand. [³H]spiperone was bound specifically to sections of control innervated kidneys with a dissociation constant (K(d)) value of 0.07 ± 0.003 nM and a maximum density of binding sites (B(max)) value of 35.4 ± 0.16 fmol/mg tissue. Light microscope autoradiography showed the accumulation of silver grains both in the arterial tree and in cortical tubules. At the vascular level, [³H]spiperone binding sites were accumulated primarily in the adventitia and in adventitia-media transitional zone. In cortical tubules, the higher density of [³H]spiperone binding sites was noticeable in proximal convoluted tubules. A few binding sites were also found in the glomerular tuft. In denervated kidneys, noradrenaline and dopamine levels were reduced by about 90% and 60% respectively in comparison with control innervated kidneys. Denervation reduced the density of [³H]spiperone binding sites by more than 85%. In denervated kidneys, light microscope autoradiography showed the disappearance of specific vascular binding sites and a remarkable reduction of tubular [³H]spiperone binding sites. The above results indicate that the largest majority of renal dopamine D₂-like receptors labelled by [³H]spiperone is prejunctional in location.