The Mechanism of Adrenergic Alpha 2 Receptor Activation - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
USMLE Articles
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam

Thread Tools Search this Thread Display Modes
Old 12-17-2011
USMLE Forums Addict
Steps History: Not yet
Posts: 108
Threads: 15
Thanked 22 Times in 13 Posts
Reputation: 32
Question The Mechanism of Adrenergic Alpha 2 Receptor Activation

Adrenergic alpha2 receptor activaton: causes platelets aggregation whats the mechanism?
Reply With Quote Quick reply to this message

Old 12-17-2011
USMLE Forums Scout
Steps History: 1 + CK
Posts: 99
Threads: 8
Thanked 32 Times in 28 Posts
Reputation: 42

Adrenaline or UK 14304 (a specific alpha 2-adrenoceptor agonist) and phorbol ester (phorbol 12,13-dibutyrate; PdBu) or bioactive diacylglycerols (sn-1,2-dioctanoylglycerol; DiC8) synergistically induced platelet aggregation and ATP secretion. The effect on aggregation was more pronounced than the effect on secretion, and it was observed in aspirinized, platelet-rich plasma or suspensions of washed aspirinized platelets containing ADP scavengers. No prior shape change was found. In the presence of adrenaline, DiC8 induced reversible aggregation and PdBu evoked irreversible aggregation that correlated with the different kinetics of DiC8- and PdBu-induced protein kinase C activation. Adrenaline and UK 14304 did not induce or enhance phosphorylation induced by DiC8 or PdBu of myosin light chain (20 kDa), the substrate of protein kinase C (47 kDa), or a 38 kDa protein. Immunoprecipitation studies using a Gcommon alpha antiserum or a Gi alpha antiserum showed that Gi alpha is not phosphorylated after exposure of platelets to PdBu or PdBu plus adrenaline. Adrenaline, PdBu or adrenaline plus PdBu did not cause stimulation of phospholipase C as reflected in production of [32P]phosphatidic acid. Adrenaline caused a small increase of Ca2+ in the platelet cytosol of platelets loaded with Indo-1; this effect was also observed in the absence of extracellular Ca2+. However, under conditions of maximal aggregation induced by adrenaline plus PdBu, no increase of cytosolic Ca2+ was observed. Platelet aggregation induced by PdBu plus adrenaline was not inhibited by a high intracellular concentration of the calcium chelator Quin-2. These experiments indicate that alpha 2-adrenoceptor agonists, known to interact with Gi, and protein kinase C activators synergistically induced platelet aggregation through a novel mechanism. The synergism occurs distally to Gi protein activation and protein kinase C-dependent protein phosphorylation and does not involve phospholipase C activation or Ca2+ mobilization.
Reply With Quote Quick reply to this message



Quick Reply

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Where you live. Leave blank if you don't want to tell.


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
TSH Subunits and Receptor Activation! saintdizzy USMLE Step 1 Forum 0 10-08-2011 08:50 AM
Platelet Activation Steps apx85 USMLE Step 1 Bits & Pieces 0 05-19-2011 11:38 AM
Toll-Like Receptor 4 Activation fin-84 USMLE Step 1 Forum 3 11-03-2010 10:54 PM
Mnemonic RiRi to remember Alpha and Beta receptor effects on Insulin and Renin raheel_memon USMLE Step 1 Mnemonics 1 07-22-2010 04:17 PM
Trypsinogen activation peptide MLE-Love USMLE Step 2 CK Buzzwords 0 02-25-2010 07:49 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)