Orellanine inhibits protein synthesis in Madin-Darby canine kidney cells, in rat liver mitochondria, and in vitro: indication for its activation prior to in vitro inhibition.

Pure orellanine, a nephrotoxic compound extracted from the mushroom Cortinarius orellanus, which is known to induce severe kidney damage several days or weeks after ingestion, is found to inhibit strongly the synthesis of macromolecules (proteins, RNA and DNA) in Madin-Darby canine kidney (MDCK) cells and in rat liver mitochondria, although the uptake of labelled precursors of the above macromolecules is not significantly altered. Direct addition of orellanine to a cell-free system of rabbit reticulocyte lysate does not produce any inhibition of protein synthesis. However, when orellanine is pre-incubated with activating rat liver microsomal systems, this inhibition occurs. Thus, the in vivo inhibition of protein synthesis is most likely due to a metabolite of orellanine.