Ammonia formation in the medicinal leech, Hirudo medicinalis--in vivo and in vitro investigations.

1. The excretion of N compounds was investigated in leeches fed various test solutions. 2. Ingestion was followed by a striking increase of NH3 release exhibiting a characteristic time-course. 3. The NH3 excreted resulted from the degradation of N compounds present in the test solutions. 4. Formation of NH3 from proteins was inhibited by kanamycin, but was unaffected in the case of amino acids. 5. Symbiotic microorganisms do not significantly contribute to NH3 formation. 6. Glutamate dehydrogenase and AMP deaminase are the enzymes most likely to be responsible for NH3 formation in Hirudo.