Induction of reverse flow of Na+ through the active transport pathway in toad urinary bladder.

When active Na+ transport across the toad urinary bladder was abolished by ouabain, a 'reversed' short circuit current could be induced by an Na+ concentration gradient. This reversed current was increased by vasopressin and inhibited by amiloride and appears to represent net Na+ movement 'backwards' through epithelial cells which normally participate in active Na+ transport across the bladder.