VPT 421: Veterinary Toxicology (2+0)

Specific Mechanisms of Intoxication

SPECIFIC MECHANISM OF INTOXICATION

• Specific mechanisms of intoxication include
  • Chemical injury – e.g. Corrosives, caustics
  • Necrosis of epithelial cells resulting in energy deficit and ischemia
  • Inhibition of / or competition with enzymes like cholinesterase
  • Interference with body metabolism or synthesis like uncoupling of oxidative phosphorylation, inhibition of oxidative phosphorylation, inhibition of nucleic acid and protein synthesis and interference with fat mobilization
  • Functional effects on the nervous system like enhanced reflexes, change in permeability of nerve cell membranes to ions and inhibition of enzymes
  • Lesions of the central and peripheral nervous systems like neuronal necrosis, demyelination and impaired transport within the axon itself
  • Injury to the blood and vascular system like hypoplasia and aplasia of cellular components, reduced synthesis of haemoglobin, formation of methhaemoglobin, oxidative denaturation of haemoglobin, formation of carboxyhaemoglobin and coagulopathy
  • Exposure of agents with actions similar to normal metabolites or nutrients
  • Immunosuppression
  • Developmental effects
  • Carcinogenesis

• In the normal drug action when a ligand binds with the receptor a positive response is produced. Sometimes a toxicant inactivates a receptor and by inactivation of the receptor, no response is elicited when a ligand binds with the receptor. This is shown as toxicant A action. In other instances, a toxicant competes with the ligand for the same receptor site, and when the toxicant occupies the receptor, it prevents the ligand from binding and thereby no response is produced. This is exhibited in toxicant B action.