At very low concentrations,epinephrine causes an artery to vasodilate.At higher concentrations epinephrine causes the same artery to constrict.How can these different effects be explained?
A)There is one type of epinephrine receptor that uses two second messenger systems
B)There are two types of epinephrine receptors with different affinities for epinephrine that use two different second messenger systems
C)There are two types of receptors for epinephrine that use the same second messenger system
D)At higher concentrations epinephrine can pass through the plasma membrane and directly stimulate contraction within the cell

Question

Quizplus · Accepted Answer

There are two types of epinephrine receptors with different affinities for epinephrine that use two different second messenger systems. At low concentrations, epinephrine selectively binds to the beta-2 adrenergic receptor, which leads to the production of cyclic AMP, causing vasodilation. At higher concentrations, epinephrine also binds to the alpha adrenergic receptor, which leads to the production of inositol trisphosphate and intracellular calcium release, causing vasoconstriction. Therefore, the dual effects of epinephrine are due to its differential binding to the two types of receptors with different sensitivities to the hormone.

At Very Low Concentrations,epinephrine Causes an Artery to Vasodilate