Postnatal development of dopamine D1-like and D2-like receptors in the rat kidney: a radioligand binding study.

Dopamine exerts important natriuretic and renal haemodynamic changes mediated through the interaction with dopamine D1-like and D2-like receptors. Dopamine-mediated natriuresis and renal vascular effects are less in younger than in older animals. The pharmacological profile and the density of dopamine D1-like and D2-like receptors were assessed in the kidney of rats ranging from 2 to 90 days of age by using radioligand binding assay techniques. [3H]SCH 23390 was used as ligand of dopamine D1-like receptors. [3H]Spiperone was used as a ligand of dopamine D2-like receptors. The dissociation constant (Kd) value of [3H]SCH 23390 binding was slightly decreased from the 21st day of age in comparison with animals of 2 and 7 days of age. The maximum density (Bmax) of [3H]SCH 23390 binding sites increased progressively until the 21st day of age and then plateauned. A similar trend was found for [3H]Spiperone binding sites. In [3H]Spiperone binding experiments, the Kd value was remarkably decreased from the 21st to the 90th day of life. Bmax value of [3H]Spiperone binding sites were similar in rats of 2 and 7 days of age and subsequently increased to values similar to those found in adult rats from the 21st day of life. The pharmacological profile of [3H]SCH 23390 and [3H]Spiperone was similar in rats of the different ages investigated. These findings suggest that renal dopamine D1-like and D2-like receptors undergo maturational changes in the first 3 weeks after birth and then are stabilized at the adult levels. The possibility that the increased expression of renal dopamine receptors postnatally may be linked with the gradual appearance of dopamine-mediated renal responses after birth is discussed.