THE RENAL DOPAMINERGIC SYSTEM IN AGING

1 The kidney contains rather large stores of dopamine (DA) (both neuronal and non-neuronal) and is rich in DA-1 and DA-2 receptors. However, no information is so far available as to the age-related changes of the renal dopaminergic system. 2 DA-1 receptors were studied in the kidney of young (3-month-old), adult (12-month-old) and aged (27-month-old) male Wistar rats using radioreceptor binding and autoradiographic techniques. [H-3]-SCH 23390 was used as a ligand. 3 Binding studies demonstrated a significant loss in the density but not in the affinity of [H-3]-SCH 23390 binding in sections of kidney of adult animals in comparison with young animals. A further decrease in the density of DA-1 binding sites was noticeable in aged rats in comparison with adult rats. 4 Autoradiography revealed that in the kidney [H-3]-SCH 23390 binding sites are located primarily within the proximal cortical tubules and, in lesser amount, within the distal cortical tubules and the smooth muscle of the intrarenal arteries. Ageing is accompanied by a more remarkable loss of tubular than vascular DA-1 receptors. 5 These findings suggest that the renal DA-1 receptor system is impaired with age similarly as described for the striatal D-1 receptor system.