Polyribosome disaggregation in rat liver following administration of the phytotoxic proteins, abrin and ricin.

As the possible mechanisms of inhibition of protein biosynthesis, it was demonstrated that the toxic proteins abrin and ricin cause the degradation of polyribosomes of rat liver or Ehrlich ascites tumor cells. Abrin and ricin have no direct effect on the structural and functional integrity of polyribosomes but act indirectly by increasing the RNase activity in the postmicrosomal supernatant fractions of rat liver or Ehrlich ascites tumor cells. These increases of RNase activity coincided in time with reduction in the amino acid incorporation and degradation of polyribosomes in vivo and the ultrastructural changes in the rough endoplasmic reticulum of hepatic parenchymal cells.