Tox Exam 2 MOAs

Question 1

What is the MOA of phenoxy derivatives/2,4-D?

Answer 1

alters the metabolism of plants, which increases their toxicity by increasing accumulation of nitrate or cyanide.

Question 2

what is the MOA of paraquat and diquat (dipyridyl herbicides)?

Answer 2

dipyridyl reduced by NADH to produce singlet oxygen = produces free radicals in the LUNGS

Question 3

what is the MOA of PCP?

Answer 3

blocks ATP –> increases O2 demand = overheating CNS stimulation

Question 4

what is the MOA of NPN?

Answer 4

ammonia inhibits the citric acid cycle resulting in lack of energy, decreased cellular respiration and tissue damage

Question 5

what is the MOA of ionophores?

Answer 5

influx of sodium-ionophore complex into the mitochondria, sequestration of Ca inside and inhibition of ATP

Question 6

what is the MOA of water deprivation/Na ion toxicity?

Answer 6

high sodium in the brain inhibits anaerobic glycolysis resulting in lack of energy necessary for active transport of Na out of the brain

Question 7

what is the MOA of inorganic arsenic?

Answer 7

trivalent binds to lipoic acid to slow glycolysis and citric acid cycle

Question 8

what is the MOA of organic arsenic (roxarsone and arsanilic acid)?

Answer 8

peripheral nerve degeneration similar to VitB toxicity

Question 9

what is the MOA of copper toxicosis?

Answer 9

Cu accumulation in the liver causes degeneration and necrosis. release of cu causes RBC membrane damage resulting in hemolytic crisis or oxidation to methemoglobin

Question 10

what is the MOA of Molybdenum toxicosis?

Answer 10

toxicity is due to COPPER deficiency! Cu is involved in hematopoiesis, connective tissue metabolism, myelin formation in newborns, pigmentation, and bone formation

Question 11

what is the MOA with Selenium toxicosis?

Answer 11

1. Acute –> irritation of GI mucosa. death due to resp insufficiency from pulmonary edema.
2. chronic –> decrease ATP, starvation, thirst, weakness, blindness

Question 12

what is the MOA with lead toxicosis?

Answer 12

breakdown of the BBB through toxic effects on the endothelial cells and alteration of microvascular systems resulting in brain edema

Question 13

what is the MOA with zinc toxicosis?

Answer 13

unknown, but causes intravascular hemolysis with a secondary zinc mediated renal injury

Question 14

what is the MOA with iron toxicosis

Answer 14

free iron ions are very reactive causing free radical peroxidation. primary effects are on GIT, CV, and liver

Question 15

what is the MOA of industrial petroleum?

Answer 15

1. GI - directly irritating and erodes epithelium leading to increased absorption
2. systemic effects: CNS, depression, liver/kidney damage, cardiac arrhythmia and arrest
3. ASPIRATION PNEUMONIA - ingestion leads to vomiting and AP - direct contact causes dissolution to lipid membranes, cell swelling, pulmonary edema, bronchoconstriction and necrosis
4. inhalation causes chemical pneumonitis

Question 16

what is the MOA of detergents?

Answer 16

direct irritation of skin and MM and may also cause NM paralysis

Question 17

what is the MOA of phenols?

Answer 17

direct denature and precipitation of proteins that lead to coagulative necrosis

Question 18

what is the MOA of bleaches?

Answer 18

combines with stomach acids to form hypoclorous which leads to local coagulation

Question 19

what is the MOA of zinc phosphide?

Answer 19

inhibits oxidation and cellular energy thus creating ROS and resulting in oxidative stress

Question 20

what is the MOA of fluoroacetate (compound 1080)?

Answer 20

inhibits energy production in the citric acid cycle which results in energy depletion, citric and lactic acid accumulation and decreased blood pH

Question 21

what is the MOA of strychnine?

Answer 21

glycine antagonist (inhibitory NT) which causes continued neuronal excitability and exaggerated reflex arc of the spinal cord without convulsions

Question 22

what is the MOA of cholecalciferol?

Answer 22

Cholecalciferol is metabolized in the liver to Calcidiol which is the main inactive form in circulation, then taken to the kidney to be metabolized to Calcitriol. Calcitriol stimulates production of calcium binding protein (CBP) which increases release from bone, intake from GI and reabsorption of calcium in the kidney.

Question 23

what is the MOA of bromethalin?

Answer 23

1) Uncouples oxidation phosphorylation in the brain and spinal cord (resulting in decreased ATP production) 2) Cerebral and spinal edema that increases CSF pressure and causes neurologic dysfunction.

Question 24

what is the MOA of anticoagulant rodenticides?

Answer 24

inhibit vitamin K epoxide reductase. leads to depletion of vitamin K and coagulation factors (1972)

Question 25

what is the MOA of ethylene glycol?

Answer 25

direct irritation, CNS depression, osmotic diuresis, ARF

Question 26

what is the MOA of propylene glycol?

Answer 26

Usually NOT metabolized to toxic metabolites, causes osmotic diuresis, CNS depression, Encephalopathy and Heinz body anemia in cats.

Question 27

what is the MOA of ethanol?

Answer 27

Irritation of mm. Induces vomiting, CNS depression, vasodilation, metabolic acidosis, inhibition of ADH. NO blindness in dogs in contrast to people.