Lead Flashcards
T/F: Lead is not readily degraded in the environment
TRUE
it is persistent
T/F: Lead is readily absorbed and metabolized
False
only about 1-2% if absorbed from the GIT because it forms insoluble compounds
What pH conditions favor lead dissolution?
Acidic
What sources of lead are pets exposed to?
Most common source is lead based paints
A thumbnail sized chip of paint could have 50 - 200 ppm lead in it
other: batteries, putty, galvanized wire, lead shots, linoleum
**areial emission from combustion of leaded fuel, insecticides/herbicides
What is more readily absorbed, organic lead or inorganic lead?
Organic lead bc it is lipid soluble
Can be absorbed by the skin and accumulated in fat
What is organic lead used for?
Anti-knocking agents in gasoline products
Where is inorganic lead found?
in dyes, paints, and pesticides
Poor absorption due to low water solubility
What is the lowest lethal dose of lead in dogs?
191 mg/kg
What animals are most vulnerable to lead toxicosis related deaths?
Waterfowl
ingest spent pellets or lost fishing sinckers
Birds shot with lead pellets can become a source of secondary poisoning for other animals
What two ions will lead displace in the blood?
Ca and zinc
What dogs are most sensitive to lead poisoning?
Puppies are more sensitive than adults due to the permeability of the BB
What are the routes of lead absorption?
Dermal - organic based is absorbed better this way than inorganic
Inhalation and absorption via lungs - arial spraying of lead based pesticides (not in US)
**Ingestion* - oral absorption is poor, but increased absorption in GIT due to acidic pH
What molecules will decrease the absorption of lead in the GIT?
Calcium, zinc, and protein
Lead is absorbed by active transport using the same carrier protein as calcium
If a patient is deficient in ____, then lead is more readily absorbed
Vitamin D
Calcium
Zinc
Iron
In what animals is GIT absorption of lead greatest?
Immature animals
up to 50% compared to 5-15% in adults
Does lead cross the BBB or placental barrier?
YES
crosses BBB in young animals
What does lead bind to for transport in systemic circulation?
Binds to erythrocyte membrane (60-90% RBC binding depending on species)
Lead can stay in the soft tissue for ____ weeks
4-6
Where can lead be stored in the body for years?
In the active bone matrix compete with Ca
larger amounts in young (83-95%) vs old (70-75%)
Biologically inactive in the bone but can be released back into systemic circulation due to fracture etc
What chelating liver protein involved in cellular detoxification of inorganics, will sequester lead when it is in high concentrations?
Metallothionein
Where is lead excreted?
Primarily through the urine
Bile and milk as well
What are the target tissues of lead toxicosis?
GIT, blood, CNS
What is the MOA of lead toxicosis?
Interferes with biological structure and function
Can substitute for Ca, Zn, Mg, Fe
Competes with Ca in the bone and alters Ca movement across membranes –> Alters structure of the cerebral endothelium - edema
What is the MOA in chronic lead toxicosis?
Chronic low exposures - inhibites heme synthesis that leads to anemia (also decreased RBC lifespan)
inhibits regulation of Ca
Alters release of neurotransmitters (dopamine, acetylcholine, GABA)
**breakdown of BB via injury to endothelial cells and alteration of the microvascular systems
