POSTNATAL-DEVELOPMENT OF DOPAMINE D-1-LIKE AND D-2-LIKE RECEPTORS IN THE RAT-KIDNEY - A RADIOLIGAND BINDING STUDY

Dopamine exerts important natriuretic and renal haemodynamic changes m ediated through the interaction with dopamine D-1-like and D-2-like re ceptors. Dopamine-mediated natriuresis and renal vascular effects are less in younger than in older animals. The pharmacological profile and the density of dopamine D-1-like and D-2-like receptors were assessed in the kidney of rats ranging from 2 to 90 days of age by using radio ligand binding assay techniques. [H-3]SCH 23390 was used as ligand of dopamine D-1-like receptors. [H-3]Spiperone was used as a ligand of do pamine D-2-like receptors. The dissociation constant (K-d) value of [H -3]SCH 23390 binding was slightly decreased from the 21st day of age i n comparison with animals of 2 and 7 days of age. The maximum density (B-max) of [H-3]SCH 23390 binding sites increased progressively until the 21st day of age and then plateauned. A similar trend was found for [H-3]spiperone binding sites. In [H-3]spiperone binding experiments, the K-d value was remarkably decreased from the 2lst to the 90th day o f life. B-max value of [H-3]spiperone binding sites were similar in ra ts 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 pharmacol ogical profile of [H-3]SCH 23390 and [H-3]spiperone was similar in rat s of the different ages investigated. These findings suggest that rena l dopamine D-1-like and D-2-like receptors undergo maturational change s in the first 3 weeks after birth and then are stabilized at the adul t levels. The possibility that the increased expression of renal dopam ine receptors postnatally may be linked with the gradual appearance of dopamine-mediated renal responses after birth is discussed. (C) 1997 Elsevier Science Ireland Ltd.