nirvanamona
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E
phospholambam increases activity of Ca pump of the sarcoplasmic reticulum, increasing the speed of Ca re-accumulation in the sarcoplasmic reticulum. Net result is to increase contractility and shorten time of contraction.
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| giovanni83
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no..it's not E
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| nirvanamona
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honestly never really knew bout MOA of phospholambam so gotta thank you for posting this excellent Q. my further reading makes me understand the Q better. what i found out was that:-
a) NE/E binds to adrenegic receptors in the heart and cause the usual response of stimulating the adenylate cyclase and converting ATP to cAMP which inturn activates protein kinase A.
b) protein kinase A phosphorylate the calcium channels and cause calcium influx. apart from that it also phosphorylates phospholambam, an inhibitory protein. Normally phospholambam keeps the calcium pump at a low activity level. with adrenergic stimulation i.e. when protein kinase A phosphorylates phospholambam the inhibitory action is lifted and so allows calcium pump to act maximally.
c) this results in more calcium influx with each heart beat i.e. more larger and quicker contractions.
the above explains the actions on heart muscle via beta 1 agonist
however it is said the opposite events happen with smooth muscle via beta 2 agonist activity...i.e. decrease contraction etc.
having said all this...the answer now points to B? decreases the duration of contraction....because of increased contractility???
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| giovanni83
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yes right! 
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| nirvanamona
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COOL
once again...execellent Q. THANKS
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| drpkaur
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nice ques..
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| young_doc
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Had never heard of phospholambin.. thanx!!!
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| khorshid
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me too , interesting
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| muzammil
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nice question
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| MRMAVERICK
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