Cortical tubular and glomerular dopamine receptors in the rat kidney.

Dopamine receptors in glomeruli and renal cortical tubules were characterized using radioligand binding and adenylate cyclase studies. The binding of [3H]haloperidol to glomeruli and tubules was rapid, saturable with time and ligand concentration, reversible, of high affinity, and demonstrated stereoselectivity and antagonist and agonist rank potency for binding to dopamine receptors. Analysis of kinetic data and Rosenthal plots in glomeruli revealed a single class of [3H]haloperidol binding sites with an apparent dissociation constant (Kd) of 6 nM and maximum receptor density (Bmax) of 0.42 pmol/mg protein. In tubules, at least two binding sites were noted, one with an apparent Kd of 38 nM and Bmax of 1.90 pmol/mg protein and another with an apparent Kd of 183 nM and Bmax of 3.50 pmol/mg protein. Dopamine and apomorphine increased adenylate cyclase in tubular membranes while no increases were noted in glomeruli. These studies suggest that glomeruli have D2 dopamine receptors, while renal cortical tubules contain the D1 dopamine receptor.