Ricin does not act as an endonuclease on L cell polysomal RNA

The ability of ricin to act as an endonuclease was examined using labelled polysomes isolated from mouse L cells grown in [³²P] orthophosphate. No change was detected in the electrophoretic mobility of any ribosomal RNA species whether L cells were first treated with ricin or the isolated polysomes were treated with ricin. No trichloroacetic acid soluble counts over control levels were released by ricin treatment of isolated polysomes and no changes were observed in sucrose density gradient polysome profile with ricin treatment. The action of ricin on polysomes which results in inhibition of translation does not appear to involve endonuclease activity.