What is the mechanism by which ionophores exert toxicity?

• A. Inhibition of acetylcholinesterase
• B. Interference with K and Ca transport
• C. Direct hepatotoxicity via CYP induction
• D. Activation of GABA receptors

Answer: (B)

Ionophores cause toxicity by disrupting ion homeostasis across cellular membranes. They act as mobile carriers or pore-forming agents that shuttle ions, especially potassium and calcium, across lipid bilayers, bypassing normal channels. This collapses essential ion gradients, leading to calcium overload and membrane potential disturbances. Elevated intracellular Ca2+ activates destructive enzymes, impairs mitochondria and ATP production, and damages muscle and heart tissues. The net result is energy failure and cellular injury, which is the hallmark of ionophore toxicity. The other mechanisms listed don’t fit the pattern of ionophore effects: acetylcholinesterase inhibition would cause cholinergic symptoms, direct hepatotoxicity via CYP induction isn’t characteristic, and GABA receptor activation would affect the CNS rather than produce the observed muscle/heart toxicity.