Gossypol affects ion transport in the isolated intestine of the seawater adapted eel, Anguilla anguilla

Cottonseed (Gossypium sp.) meals are protein rich and inexpensive, but the presence of the polyphenolic dialdehyde, gossypol, is responsible of many toxic effects in animals including fishes. Recently an effect on the transepithelial ion transport in rat colon has been demonstrated. In this study we investigated the effect of gossypol on the transepithelial electrical parameters of the isolated intestine of seawater adapted eel, Anguilla anguilla, by employing a Ussing chamber technique. We showed that the addition of gossypol to the perfusion media reduced short circuit current (Isc), a measure of Cl− active absorption in this tissue, and increased tissue conductance (gt). The observation that the effect of gossypol on both Isc and gt was modified by the pretreatment with TFP, a calmodulin inhibitor, suggests that the substance acts via a Ca2+ calmodulin pathway and excludes the possibility that the observed effects were due to a cytotoxic action. In addition, experiments performed in the presence of verapamil suggest that the polyphenolic pigment increases Ca2+ influx. It is likely that gossypol stimulates a basolateral quinine sensitive K+ conductance producing a K+ flux in absorptive direction that explains the reduction of Isc. In addition dilution potential experiments showed that the polyphenolic aldehyde increases the anion conductance of the paracellular pathway. In conclusion our study suggests that gossypol alters ion transport in eel intestine by acting on both transcellular and paracellular pathways. Since the intestine is an important organ for maintaining the water and ion balance in seawater adapted fish, it is conceivable that gossypol could impair the ability of the animals to adapt to the environment.