Ca?? - dr_oso

[ArchivalUser]

In order to study calcium fluxes in living cells, a researcher employs fluorescent calcium indicators
and laser scanning confocal microscopy. In her experiments, she stimulates smooth muscle cells using a
variety of pharmacological agents, then videotapes the calcium fluxes in the cell in real time using the
confocal microscope. Which of the following drugs would most likely produce the strongest calcium signal
in the smooth muscle cells?

A. Clonidine

B. Isoproterenol

C. Phentolamine

D. Phenylephrine

E. Timolol

[ArchivalUser]

d.

[ArchivalUser]

d...........

[ArchivalUser]

D...

[ArchivalUser]

D.

[ArchivalUser]

yessssss dddddd everyone very good

[ArchivalUser]

plz explain why d??

[ArchivalUser]

alpha 1 agonist. through IP3 pathway.

[ArchivalUser]

thanx

[ArchivalUser]

The correct answer is D. Two pieces of information are necessary to answer this question. First,
you must know the drug classes represented by the answer choices. Second, you must know what
second messengers are associated with these receptors. Phenylephrine is an α1 agonist;
α1 receptors are coupled to Gq, which stimulates phospholipase C (PLC), leading to
hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2), a phospholipid in the plasma
membrane. PIP2 is split into two second messengers: inositol-1,4,5-triphosphate (IP3) and
diacylglycerol. IP3 diffuses through the cytoplasm to internal storage sites, where it triggers
the release of calcium, thus providing the signal for this experiment. Diacylglycerol remains in
the membrane and activates protein kinase C.