Toxic Effects of Metals Flashcards
Methylation of arsenic produces what compound(s)? What are the advantage and disadvantage of this metabolic process?
Methylation of arsenic (as arsenite) leads to the formation of methyarsenite (MMA) and dimethylarsenite (DMA). The advantage is that this promotes short-term excretion but may increase chronic health risks from internal doses of MMA and DMA.
Aside from death, acute arsenic toxicity includes what signs and symptoms?
Hepatomegaly, cardiac arrhythmia, terminal cardia failure, GI irritation and intestinal sloughing.
Arsenic has several chronic health effects including skin keratosis, inflammation and peripheral neurotoxicity. It is also associated with cardiovascular disease. What is the prevailing theory behind the cardiovascular effects of arsenic?
Induction of atherosclerosis, enhance existing vessel diseases and prolonging of the cardiac Q-T potential.
What is the difference in the mechanism of action between trivalent and pentavalent arsenic species?
Trivalent arsenic species are thiol reactive and alter protein activity by reaction with thiol groups on proteins. Pentavalent arsenic species mimic phosphate and compete in phosphate-dependent processes.
What is the primary route of exposure to beryllium?
a) Ingestion of contaminated drinking water
b) Ingestion of food items with beryllium
c) Inhalation in occupational settings
d) Dermal contact with dusts, soil and water
c) Inhalation. Beryllium is a divalent metal that is used in a vareity of industrial processes and this is where most exposures occur.
What are the characteristics of chronic beryllium disease (CBD) or berylliosis?
CBD is a granulomatous inflammation of the lungs that leads to respiratory issues including difficulty breathing (dyspnea) after exertion. This is immune system mediated, and may occur after initial sensitization from exposure to beryllium.
Where is beryllium primarily stored in the human body? What is the long-term implication?
Beryllium is primarily stored in bone, meaning it’s slow release may sustain low internal doses for chronic exposures. This may lead to sustained immunological (inflammation) responses.
Cadmium is found in a variety of environmental sources. Between inhalation and ingestion, which route of exposure delivers the higher proportion of the external dose? Why?
Inhalation (e.g. cigarette smoking or industrial dusts) delivers a higher proportion of the dose than ingestion. Ingestion reduces the proportion of uptake due to competition with iron and calcium, as well as interference from dietary proteins.
Which organ does cadmium primarily concentrate in over the course of chronic exposure? What is the toxicological effect?
Cadmium primarily concentrates in the kidney, leading to impaired renal function. This includes tubular and glomerular dysfunction, followed by interstitial nephritis. This leads to leakage and increases urinary excretion of glucose, amino acids, calcium and enzymes.
What are the two predominant forms of chromium? Which is more toxic?
Trivalent and hexavalent chromium. Hexavalent chromium is more toxic, like due to formation of ROS, whereas trivalent is also an essential nutrient for glucose metabolism.
Deficiencies of which nutrients lead to increase lead (Pb) absorption in children?
Zinc, manganese, iron and calcium
What does lead (Pb) interfere with the synthesis of, thereby leading to hematological toxicity?
Lead (Pb) prevent porphyrin synthesis, thereby disrupting heme synthesis. This observed through
How can lead (Pb) impair Vitamin D synthesis?
Leab (Pb) in the kidney disrupts porphyrin synthesis and there is a porphyrin-dependent enzyme in the kidneys that regulates Vitamin D synthesis.
What is major target organ for mercury vapor? What is the triad of symptoms associated with exposure?
Lungs and nervous system. The triad includes tremors, gingivitis and erethism.
Erethism includes memory loss, excitability, insomnia, depression and shyness)
What is the major target of inorganic mercury?
Inorganic mercury targets the kidney, where is accumulates after exposure and the reduction of inhaled mercury. It is nephrotoxic with some forms being dependent on immune reactions. The mechanism likely involves thiol binding by divalent Hg.
