Alpha- Adrenoceptors in the Developing Kidney

Summary MATERIALS AND METHODS The maturation of renal alpha-adrenoceptors was investigated in dogs. Alpha-adrenoceptors were characterized by radioligand binding using the alpha-1-adrenergic antagonist, [3HI-WB-4101. In renal olasma membranes obtained from the outer cortex of neonates,-the binding of the ligand was rapid, reversible, of high affinitv. saturable. and ", stereoselective. The com~etition studies with adrenergic agonists and antagonists were indicative of alpha- receptors. In puppies less than 1-w-old, the binding affinity of 13H] -WB-4101 (Ka = 0.638 f 0.17 nM) was greater than 3-5 week-old puppies (Kd 1.573 + 0.315 nm); (P < 0.05), but receptor number was similar (63.75 + 19.1 versus 79.10 + 5.99 fmole/mg protein). No consistent specific binding could be demonstrated in plasma membranes obtained from inner cortex or medulla. In the adult dog, no consistent specific binding could be demonstrated for plasma membranes obtained from any region of the kidney. These studies indicate that during maturation there is a decrease in alpha-adrenoceptor density and affinity in membranes from the outer cortex of the kidney.