Cadmium chloride injected to mice (20 micronmoles/kg) provokes in the livers a degradation of polyribosomes and diminishes their protein synthetic ability measured in vitro. CdCl2 added in a final concentrations between 30 and 100 micron to the protein synthetic cell-free system derived from livers of control mice inhibits its activity.

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Polyribosome sedimentation pattern and their in vitro protein synthetic ability were investigated in kidneys of mice treated with a single injection of HgCl2. Mercury bichloride, after 1 h, evokes polyribosome disaggregation, the extent of which is logarithmically correlated with the dose in the range of 2.5-20 micromoles/kg. With the dose of 2.5 micromoles/kg the effect occurs in 1 h, it is maximal between 1 h and 3 h. After 6 h polyribosomes are reaggregated. Cycloheximide pretreatment does not prevent the HgCl2 induced disaggregation of kidney polyribosomes. The cell-free system derived from kidneys of HgCl2 treated mice (10 micromoles/kg, 1 h) has a decreased protein synthetic ability. Both, in livers of mice treated with 20 micromoles/kg HgCl2 and in isolated rat's reticulocytes incubated with 20 micro M HgCl2 during 1 h there were no apparent changes in the polyribosome sedimentation patterns.

Insulin-induced hypoglycemia provokes polyribosome disaggregation and accumulation of monomeric ribosomes in the brain of rats with hypoglycemic paresis and coma. The extent of brain polyribosome disaggregation depends on the decrease of blood glucose concentration, and in comatose animals on the duration of hypoglycemia. Cycloheximide prevents the disaggregation of brain polyribosomes induced by hypoglycemia, indicating that hypoglycemia affects brain protein synthesis, decreasing the rate of initiation relative to the rate of elongation of polypeptide chain synthesis.

The distribution of ribosomes between their various functional states (native subunits, unprogrammed ribosomes, monoribosomes and polyribosomes) was analyzed in livers of cadmium-treated (CdCl₂ 20 µmol/kg, 1 h) and control mice. The ribosomes with double-labelled RNA were separated by sucrose density-gradient centrifugation in zonal rotor, and monomeric ribosome fraction was subsequently isolated and analyzed by selective dissociation of unprogrammed ribosomes. The analysis shows that the increase in monomeric ribosomes, occurring during polyribosome disaggregation in livers of cadmium-treated mice, is entirely due to the increase of the unprogrammed ribosome fraction at the expense of polyribosomes. Protein synthetic activity of polyribosomes in vivo in livers of cadmium-treated and control mice were compared by double labelling of nascent and soluble polypeptides with [¹⁴C]-and [³H]-leucine. Incorporation of radioactivity was relatively higher in nascent polypeptides and lower in soluble polypeptides in cadmium-treated as compared with control mice. The results indicate that cadmium inhibits protein synthesis in livers of mice, affecting both the rate of initiation and the rate of elongation, but decreasing the former more than the latter.