Deck 6: Receptor-Mediated Toxicities on the Outside of Cells

Question 1

How does the Scatchard plot determine the potency of a given toxicant?

Answer 1

High affinity toxicants will be more potent in their toxic action as they bind as agonists or antagonists to the target receptor.

Question 2

How does kainic acid cause toxicity to mammalian neuronal cells? What common local anesthetic agent do something opposite?

Answer 2

Kainic acid targets glutamate receptors increasing Na⁺ movement into these cells (overstimulates). Lidocaine blocks Na⁺ channels and would have opposite effects at concentrations that were anesthetic.

Question 3

Why does targeting tyrosine kinase receptors lead to either cell proliferation or cell damage/death?

Answer 3

The tyrosine kinase pathway leads to cell proliferation as shown by the effect of the appetite suppression peptide obestatin on a gastric cancer cell line. However, pertussis toxin (whooping cough) has opposite effects as indicated by its partial ability to block the action of obestatin via inhibition of phosphoinositide 3-kinase.

Question 4

How can cAMP made by G-protein pathway be immunostimulatory or immunosuppressant?