Characteristics of rat kidney dopamine receptors and the effects of renal denervation and dopamine infusion on these receptors

The characteristics of dopamine receptors, as well as the effects of denervation and dopamine infusion on dopamine receptors were studied using the radiolabeled receptor assay of [³H]-spiperone on rat kidney membrane preparations. The rat renal cortex was found to have a single class of [³H]-spiperone binding sites with a dissociation constant (K(d)) of 13.5 ± 2.2 nM. However, neither sulpiride nor serotonin strongly interacted with [³H]-spiperone binding, suggesting that DA1 receptors were predominant in the rat renal cortex. Denervation was performed by surgically stripping the nerves from the renal artery and coating them with 10% phenol. Chronic denervation had no significant effect on the affinity or maximum binding capacity of the renal dopamine receptors, although diuresis and the disappearance of catecholamine fluorophores in the denervated rats were observed. Chronic infusion of dopamine was performed using an osmotic minipump, resulting in a decrease in the number of rat kidney dopamine receptors. These results suggest that the dopamine receptor subtype in the renal cortex was mainly DA1, and that the major source of dopamine which affected the dopamine receptors in the rat kidney was not the nerve ending, but rather the circulation.