Effects of diphenylamine on sodium and water transport across the toad skin and bladder

Abstract

Diphenylamine (DPA) induces cyst formation in the rat kidney. To define mechanisms by which it might act in vivo, the effects of DPA on sodium and water transport were studied in the isolated toad ( Bufo marinus) skin and urinary bladder. When DPA (5 mg/100 ml) was added in skin experiments to the outside bathing medium, the short-circuit current (SCC) decreased rapidly and reached a plateau in 40–50 min. The effect of DPA on SCC was not modified in the presence of antidiuretic hormone (ADH); nor did DPA interfere with the usual action of ADH to increase SCC. The reduction in SCC due to DPA was accompanied by a reduction in influx of Na, the magnitude of reduction in SCC being equivalent to that in net Na flux. DPA failed to alter Cl influx or outflux. In the urinary bladder with 1:5 choline chloride-Ringer on the mucosal side and full NaCl Ringer on the serosal side, the osmotic water transfer induced by ADH was significantly reduced in the presence of DPA on either the serosal or the mucosal side. These results indicate that DPA inhibits both active sodium transport and ADH-induced passive water transport in vitro. Such actions, were they to occur in vivo, could play a role in facilitating renal cyst formation.