The Non-ureogenic Stinging Catfish, , Actively Excretes Ammonia With the Help of Na/K-ATPase When Exposed to Environmental Ammonia.

The stinging catfish, , can tolerate high concentrations of environmental ammonia. Previously, it was regarded as ureogenic, having a functional ornithine-urea cycle (OUC) that could be up-regulated during ammonia-loading. However, contradictory results indicated that increased urea synthesis and switching to ureotelism could not explain its high ammonia tolerance.