Question

Dobutamine is an agonist at B1 adrenergic receptors and milrinone inhibits phosphotdiesterase 3(PDE3). However, both drugs act to change the concentration of which signaling molecule?

a. increase the concentration of Ca 2+ in the SR

b. increase the concentration of Na+ in the cytoplasm

c. decrease the concentration of Ca2+ in the SR

d. decrease the concentration of cAMP in the cytoplasm

e. Increase the concentration of cAMP in the cytoplasm

Answer 1

Dobutamine binds to B1 adrenergic receptors and leads to an increase in the concentration of cyclic adenosine monophosphate (cAMP). It does so by activating adenylyl cyclase.

Milrinone acts to inhibit phosphotdiesterase 3(PDE3). PDE3 acts to hydrolyse cAMP and degrade it. Thus, milrinone acts to prevent the breakdown of cAMP and this increases concentration of cAMP in the cytoplasm.

Thus, the correct choice should be:

Dobutamine and milrinone, both drugs act to :

Increase the concentration of cAMP in the cytoplasm.