Isoproterenol has what effect on systemic vascular resistance (SVR)?

Isoproterenol has what effect on systemic vascular resistance (SVR)?

• A. It decreases SVR
• B. It increases SVR
• C. No effect
• D. Variable

Answer: (A)

Isoproterenol is a nonselective beta-adrenergic agonist that stimulates β1 and β2 receptors. Activation of β2 receptors in vascular smooth muscle causes vasodilation, leading to a drop in systemic vascular resistance. There is no alpha-mediated vasoconstriction with isoproterenol, so the SVR decreases rather than increasing or staying the same. The β1 effects raise heart rate and contractility, but they don’t negate the vascular smooth muscle relaxation that lowers SVR. So the expected effect on SVR is a decrease.

Isoproterenol is a nonselective beta-adrenergic agonist that stimulates β1 and β2 receptors. Activation of β2 receptors in vascular smooth muscle causes vasodilation, leading to a drop in systemic vascular resistance. There is no alpha-mediated vasoconstriction with isoproterenol, so the SVR decreases rather than increasing or staying the same. The β1 effects raise heart rate and contractility, but they don’t negate the vascular smooth muscle relaxation that lowers SVR. So the expected effect on SVR is a decrease.