Oxalate crystals, kidney toxicity

Ethylene glycol, an industrial solvent and an antifreeze compound, is involved in accidental and intentional poisonings. This compound is initially oxidized by alcohol dehydrogenase and then further biotransformed to oxalic acid and other products. Oxalate crystals are found in various tissues of the body and are excreted by the kidney. Deposition of oxalate crystals in the kidney causes renal toxicity. Ethylene glycol is also a CNS depressant. In cases of ethylene glycol poisoning, ethanol is administered to reduce the first step in the biotransformation of ethylene glycol and, thereby, prevent the formation of oxalate and other products. 

Animals may develop subacute toxicity if enough plant material is ingested to produce hypocalcemia and kidney damage, but no so much that the animal dies. With larger or more prolonged exposures, animals may experience larger deposits of calcium oxalate crystals that result in renal fibrosis or renal failure which can ultimately lead to death. 

Toxic effects due to breakdown products causing metabolic acidosis and formation of calcium oxalate crystals in kidneys and other tissues... 

The ethylene glycol and methyl alcohol (see below), which is also sometimes found in antifreeze, are poisonous because they are converted into more toxic products. Once inside the body, the ethylene glycol in the antifreeze is changed by metabolism into first one, and then several other chemicals. This requires the same enzyme that metabolizes the alcohol we consume in alcoholic drinks (ethyl alcohol). The ethylene glycol is converted into oxalic acid which is poisonous, and other poisonous products are also produced. Oxalic acid is also found in rhubarb leaves, which is what makes them poisonous. The result of these metabolic conversions is that the acidity of the blood increases (the pH decreases) and normal metabolic processes are inhibited. The oxalic acid formed can crystallize in the brain and the kidneys, causing damage. The oxalic acid also reacts with calcium and removes it from the body. The reduction of calcium... 

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