Inhibition and labeling of the rat renal Na+/H+-exchanger by an antagonist of muscarinic acetylcholine receptors.

A covalently binding label for muscarinic acetylcholine receptors, propylbenzilylcholine mustard (PrBCM), irreversibly inhibits the Na+/H+ exchanger in rat renal brush-border membrane vesicles. Substrates of the antiporter, Na+ and Li+, as well as inhibitors, amiloride, 5-(N-ethyl-N-isopropyl)amiloride (EIPA) and propranolol, protect the antiporter from inactivation by PrBCM. With [3H]PrBCM a band with an app. Mr of 65 kDa is predominantly labeled. Amiloride protects this band from labeling with [3H]PrBCM and [14C]-N,N'-dicyclohexylcarbodiimide (DCCD) proving its identity with the renal Na+/H+ exchanger. Our data reveal a specific interaction of PrBCM with the Na+/H+ exchanger and suggest structural relations between antiporter and receptors.