Response of mouse proximal straight tubule and medullary thick ascending limb to beta-agonist

Scatchard analysis of (3H)CGP-12177 and (125I)cyanopindolol (CYP) radioligand binding data revealed the presence of specific beta-adrenergic receptor-binding sites on microdissected mouse proximal straight and medullary thick ascending limb (mTAL) tubules. beta-Receptor (10(-6) M isoproterenol) stimulation of isolated perfused mTAL tubules produced a consistent hyperpolarization of the transepithelial potential that was blocked by propranolol (10(-6) M), a beta-receptor antagonist, and furosemide (10(-4) M), an inhibitor of the Na+/K+/2 Cl- triporter. In contrast, there was no electrogenic response to isoproterenol stimulation in isolated perfused proximal straight tubules. In summary, radioligand binding data show that both proximal straight and mTAL tubules possess beta-receptor-binding sites. Electrogenic transport in the mTAL can be modulated by beta-agonists, but there was no detectable electrogenic response to beta-receptor stimulation in proximal straight tubules.