Comparison of the embryotoxic effects of saporin, agrostin (type 1 ribosome-inactivating proteins) and ricin (a type 2 ribosome-inactivating protein)

The effects of two type I ribosome-inactivating proteins, saporin and agros tin, and the type 2 ribosome-inactivating protein ricin and its constituent A and B chains, on the development of cultured mouse embryos, were investi gated. Saporin and agrostin had similar embryotoxicity which was approximat ely 10(5) times weaker than that of ricin and its A and B chains, and the e mbryotoxicity of saporin and agrostin increased gradually with the dosage. In contrast, there was an abrupt rise in embryotoxictiy of ricin-A chain an d B chain as the dose was raised from 10 to 20 ng ml(-1). Saporin and agros tin did not affect the heart-beat and otic placode, but at 10 ng ml(-1) ric in and 40 ng ml(-1) ricin-A chain and B chain, all of the treated embryos e xhibited abnormalities in heart-beat, yolk sac circulation, body axis, opti c placode, otic placode, forelimb buds, branchial apparatus and cranial neu ral tube.