Palladium(II) cyanide is a chemical compound of palladium and cyanide. Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is found as a free metal alloyed with gold and other platinum group metals and in the rare minerals cooperite and polarite. (4)
belongs to the class of inorganic compounds known as transition metal nitrides. These are inorganic compounds of nitrogen where nitrogen has a formal oxidation state of -3, and the heaviest metal atom is a transition metal.
Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. Due to their ability to form strong complexes with both inorganic and organic ligands, palladium ions can disturb cellular equilibria, replace other essential ions, and interact with functional groups of macromolecules, such as proteins or DNA. Palladium complexes binding to DNA and RNA leads to strand breakage. Palladium ions are able to inhibit most major cellular functions, including DNA and RNA synthesis. Palladium compounds have been shown to bind to and inhibit various enzymes, including creatine kinase and prolyl hydroxylase. (5, 3)
Metabolism
Cyanide is rapidly alsorbed through oral, inhalation, and dermal routes and distributed throughout the body. Cyanide is mainly metabolized into thiocyanate by either rhodanese or 3-mercaptopyruvate sulfur transferase. Cyanide metabolites are excreted in the urine. Palladium may also be absorbed through oral, dermal, and inhalation exposure. Once in the body it distributes to the kidney, liver, spleen, lymph nodes, adrenal gland, lung and bone. Palladium's ability to form complexes allows it the bind to amino acids, proteins, DNA, and other macromolecules. Palladium and its metabolites are excreted in the urine and faeces. (1, 2)
Toxicity Values
Not Available
Lethal Dose
200 to 300 milligrams for an adult human (cyanide salts). (6)
No indication of carcinogenicity to humans (not listed by IARC).
Uses/Sources
Not Available
Minimum Risk Level
Not Available
Health Effects
Exposure to high levels of cyanide for a short time harms the brain and heart and can even cause coma, seizures, apnea, cardiac arrest and death. Chronic inhalation of cyanide causes breathing difficulties, chest pain, vomiting, blood changes, headaches, and enlargement of the thyroid gland. Skin contact with cyanide salts can irritate and produce sores. Contact with palladium may cause palladium sensitivity and allergy. Animal studies have shown that palladium may damage the liver and kidney. (5, 2, 3)
Symptoms
Cyanide poisoning is identified by rapid, deep breathing and shortness of breath, general weakness, giddiness, headaches, vertigo, confusion, convulsions/seizures and eventually loss of consciousness. Skin contact with palladium may cause contact dermatitis, erythema, and oedema. (5, 2, 3)
Treatment
Antidotes to cyanide poisoning include hydroxocobalamin and sodium nitrite, which release the cyanide from the cytochrome system, and rhodanase, which is an enzyme occurring naturally in mammals that combines serum cyanide with thiosulfate, producing comparatively harmless thiocyanate. Oxygen therapy can also be administered. (3)
