[125I]endothelin-1 binding to renal brush border and basolateral membranes

[125I]Endothelin-1 bound with high affinity to a single site on both brush border membranes (Kd=192+/-26 pM. Bmax=314+/-49 fmol/mg) and basolateral membranes (Kd=94.7+/-3.4 pM, Bmax=612+/-107 fmol/mg) isolated from rat renal cortex. Competition binding experiments using subtype selective ligands revealed that the proportion of ET(B) to ET(A) receptors was 80:20 and 60:40 in the brush border membrane and the basolateral membrane, respectively. The results demonstrate that endothelin-1 binds to brush border membranes, and that endothelin ET(B) receptors may be involved in the previously described effects of endothelin-1 on brush border membrane Na+ transport.