Inhibition of electrogenic sodium transport across toad urinary bladder by the mycotoxin patulin

The effects of the mycotoxin patulin (4-hydroxy-4H-furo[3,2c]pyran-2(6H)-one) on short circuited intact toad bladder and on Na+-K+, activated ATPase were examined in an attempt to elucidate the relationship between toxin, the Na+-K+ ATPase enzyme system and associated active sodium transport. Patulin inhibited transbladder short circuit current and Na+-K+ ATPase from isolated bladder preprations. The effect was exponentially dependent on time. A significantly slower rate of inhibition was achieved within 15-30 min. The results are compatible with the assumption that Na+-K+ ATPase is associated with the pump mechanism since patulin inhibited enzyme activity and concomitantly reduced the rate of electrogenic Na+ transport. A significant correlation suggested a cause-effect relationship.