Thursday, May 14, 2020

Beta 2 agonist and effect on muscles

Hello Awesomites !

I used to have a doubt why does Salbutamol cause uterine relaxation but causes contraction of skeletal muscle and cardiac muscle(tremors and tachycardia)?

Despite they have same receptors (Beta 2) how can be the action on muscle is so different.
Grossly it seems like one receptor Beta 2. This beta2 adrenergic receptor is a type of GPCR.
GPCR  are Gs, Gq ,Gi type.

Beta 2 receptor anywhere (Uterus -smooth muscle, heart- cardiac muscle, hands- skeletal muscle) is also same type of GPCR i.e Gs.

Still no difference.

Gs activates adenyl cyclase to form cAMP from ATP.
cAMP increases in all type of muscle on stimulation of Beta 2 receptor.
But it cause relaxation in smooth muscle (inhibit myosin light chain kinase)
And causes contraction of heart and skeletal muscle (activate cAMP dependent protein kinase A lead to activation of L-type calcium channel).

At one level we all may appear to be doing same thing yet at other level we are different and have our role.:)

 Happy studying !
-Upasana Y.

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