Milrinone causes systemic and pulmonary vasodilation by which action?

Milrinone causes systemic and pulmonary vasodilation by which action?

• A. Decreased cAMP in smooth muscle
• B. Increased cAMP leading to vasodilation
• C. Direct calcium channel blockade
• D. Reduced NO production

Answer: (B)

Milrinone inhibits phosphodiesterase-3, raising intracellular cAMP in vascular smooth muscle. Higher cAMP activates protein kinase A, which reduces calcium sensitivity and promotes smooth muscle relaxation, yielding systemic and pulmonary vasodilation. This vasodilatory effect comes from the increase in cAMP, not from blocking calcium channels or reducing NO production. A decrease in cAMP would tend to cause vasoconstriction, so the mechanism is clearly tied to the cAMP rise.

Milrinone inhibits phosphodiesterase-3, raising intracellular cAMP in vascular smooth muscle. Higher cAMP activates protein kinase A, which reduces calcium sensitivity and promotes smooth muscle relaxation, yielding systemic and pulmonary vasodilation. This vasodilatory effect comes from the increase in cAMP, not from blocking calcium channels or reducing NO production. A decrease in cAMP would tend to cause vasoconstriction, so the mechanism is clearly tied to the cAMP rise.