Characterization of a high affinity piretanide receptor on kidney membranes

The tritiated loop diuretic, piretanide, is a useful ligand for specific diuretic receptors which are present in the plasma membranes of renal medullary cells. Its high specific activity (30 Ci X mmol-1) made it possible to demonstrate the existence of a high affinity receptor (Kd approximately 5 nM) and a binding site with low affinity. High affinity binding is saturable, reversible and displaceable by a number of non-radioactive loop diuretics. Structural analogues, devoid of diuretic activity, do not displace piretanide binding. No specific binding occurs in liver or spleen membranes.