Heavy metal toxicity Flashcards
What are the three forms of heavy metals and which is *most toxic?
(1) Elemental - Pb
(2) *Inorganic salts - PbCl2
(3) Organic salts - (C2H5)4Pb
What are three mechanisms of heavy metal toxicity?
(1) Displacement of essential elements (ex. zinc, a cofactor for many enzymes)
(2) Formation of covalent bonds with sulfhydryl and hydroxyl groups (-SH and -OH)
(3) Carcinogenicity - arsenic, chromium, nickel, cadmium
Which heavy metals are carcinogenic?
CANCer
(1) Chromium
(2) Arsenic
(3) Nickel
(4) Cadmium
What are two modes of treatment for heavy metal intoxication?
(1) Removal of source of exposure
(2) Chelation therapy - only when levels high due to side effects
At what level of lead in blood do you get cognitive impairment?
5 mg/dl blood
What are the effects of lead poisoning?
(1) CNS - (a) impaired mental function in children and (b) lead encephalopathy (hyperactivity, ataxia, neuro deficits, seizures, coma, death)
(2) PNS effects - lead palsy, wrist drop, motor nerve dysfunction
(3) GI effects - abdominal cramps (primary symptom that brings adults to hospital), constipation
(4) Sterility
(5) Hypochromic, microcytic anemia with coproporphyrinogen and aminolevulinic acid (heme synthesis intermediates) in urine
(6) Hypertension
How can lead exposure be monitored?
(1) Coproporphyrinogen and aminolevulinic acid in urine
(2) Blood lead levels
(3) X-ray fluorescence - lead in bone with fluoresce
How can short-term lead exposure be diagnosed? Long term?
Short-term - blood lead levels
Long-term - x-ray fluorescence
What are four lead chelators?
(1) Succimer (most popular) - can be given orally, may cause severe skin rashes and diarrhea
(2) Dimercaprol - can cause hypertension/tachycardia
(3) CaEDTA - Ca exchanged with Pb, can cause kidney toxicity
(4) Penicillamine - can cause bone marrow suppression and allergic reactions to those who are allergic to penicillin
At what lead level should chelators be used for lead toxicity?
45 mg/dl
