Direct measurement of endothelin receptor in human bladder base and dome using 125I-endothelin

The amount of endothelin receptor in human bladder base and dome was measured by radioligand binding techniques using 125I-endothelin-1 (125I-ET). Specimens were obtained from 5 patients who underwent total cystectomy under diagnosis of bladder cancer. 125I-ET bound to the bladder base with the KD value of 0.004 +/- 0.003 nM and to the bladder dome with the KD value of 0.007 +/- 0.003 nM. These values were not significantly different. The Bmax values (fmol/mg protein) of 125I-ET binding to human bladder were 2.74 +/- 2.81 to the base and 47.3 +/- 9.52 to the dome. There were much larger amount of endothelin receptors in the dome compared to the base. The existence of endothelin receptors in human bladder suggests the possible roles of endothelin on the human bladder function.