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Old 07-22-2012
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Drug MOA of a drug used in BPH

A 67-year-old man comes in to the clinic stating that he has been urinating more frequently than usual. However, when he feels the urge to urinate, he has found it more difficult to start and, after he is finished, he does not feel like his bladder has fully emptied. Genital examination reveals no abnormalities, and rectal examination provides palpation of an enlarged structure with firm, rubbery nodules. Urinalysis returns no white blood cells, red blood cells, and very few bacterial colonies. Total prostate specific antigen (PSA) is 4.9 ng/mL (normal range 0–4 ng/mL), which is up from 1.7 ng/mL 2 years ago. The amount of free PSA is proportional to the increase of total PSA. Which biochemical process would be inhibited by the medication prescribed for this patient’s condition?

a) Activation of tyrosine kinase receptors
b) Hydrolysis of phosphatidylinositol
c) Stimulation of protein kinase A
d) Activation of acetylcholinesterase
e) Opening of GABA receptors
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Old 07-22-2012
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I think answer is B. hydrolysis of PIP but not sure ;-)
As I remember we give alpha 1 blockers for BPH because there are alpha 1 receptors on bladder neck and prostate which causes contraction.
So must have M receptors for Parasympathetic action. So M receptors are serpentine receptors which are attached to G protein ( don't remember which G protein- Gs or Gq)and activation of this G protein can cause hydrolysis of PIP into DAG and IP3 and then some Ca2+ calmodulin stuff which I don't remember now. Hhehehe
This seems most appropriate answer to me.
If I am wrong please correct me.
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Old 07-22-2012
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B. alpha adrenergic blocker.. They block Gq receptor Ex. Prazosin/terazosin for Rx of prostratism..

For BPH DOC is Finasteroid (5-alpha reeducate inhibitor)
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Old 07-22-2012
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its B....ALPHA 1 blockers...Gq receptors
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Matched!!!
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Ya that's right.. I applied extra science. Hehehe
Alpha 1 receptor ---- activate Gq receptor---- PIP breakdown to IP3 and DAG.


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Old 07-23-2012
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The correct answer is b) Hydrolysis of phosphatidylinositol

This pt receives alpha1-blocker. alpha1 receptor works through Gq protein -> 2nd messangers: DAG, IP3, Ca2++ -> Protein kinase C

The official explanation:

The patient is suffering from benign prostatic hyperplasia (BPH). The symptoms are caused by an enlarged prostate, which can interfere with urine functions. The increased PSA with proportional increase of free PSA indicates BPH instead of prostate cancer. Two commonly used medicines are those that inhibit 5-α reductase (to block the effects of testosterone) and those that antagonize α1 receptors (to lessen the effect of sympathetics preventing urination). Prazosin is an antagonist of mainly α1 receptors (but also acts as an antagonist of α2 receptors to a much lesser degree). The receptors are linked to different G-protein coupled receptors, and each system is connected to a different signal cascade. α1 Receptors are coupled to Gq proteins, while α2 receptors are coupled to Gi proteins. The α1-Gq protein pairing is linked to phospholipase C (PLC). Upon activation, PLC cleaves phosphatidylinositol into phosphatidylinositol 4,5-bisphophate. Activation of α2-Gi protein leads to decreased production of cyclic adenosine monophosphate (AMP). Therefore, inhibition of the α1 receptor would lead to inhibition of phosphatidylinositol bisphosphate hydrolysis.
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