Salbutamol Practical Class Flashcards

1
Q

Complete the diagram on the mechanism of action

A
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2
Q

What is the mechanism of action of salbutamol-mediated relaxtion?

A
  • Salbutamol activates the ß2 adrenoreceptor
  • The ß2 receptor is a metabotropic receptor meaning it is connected to a G protein
  • Once activated the ß2 receptor causes an increase in the activity of the enzyme adenylate cyclase
  • Adenylate cyclase catalyses the formation of cAMP from ATP
  • cAMP activates the enzyme protein kinase A (PKA)
  • PKA phosphorylates two proteins involved in smooth muscle contraction to INHIBIT their activity:
  • Inositol 1,4,5-triphosphate (IP3) Receptor which stimulates Ca2+ release from the endoplasmic reticulum
  • Myosin light chain kinase (MLCK) which phosphorylates myosin to facilitate its interaction with actin and cause contraction.
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3
Q

Complete the diagram

A
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4
Q

What is the mechanism of action for Methacholine- and histamine-mediated contraction?

A
  • Methacholine activates muscarinic 3 (M3) receptors on smooth muscle cells
  • Histamine activates H1 receptors on smooth muscle cells
  • Both M3 and H1 receptors are metabotropic and activate G proteins
  • The 2nd messenger system is same for both receptors
  • Phospholipase C is activated catalyzing the conversion of Phosphatidylinositol 4,5-bisphosphate (PIP2) to Inositol 1,4,5-triphosphate (IP3) and Diacyl glycerol (DAG)
  • IP3 activates the IP3 receptor on the endoplasmic reticulum increasing Ca2+ release which when in association with calmodulin stimulates Myosin light chain kinase (MLCK) which phosphorylates myosin to facilitate its interaction with actin and cause contraction
  • DAG activates protein kinase C (PKC) which phosphorylates Myosin Light Chain Phosphatase (MLCP) to INHIBIT its action. MLCP is responsible for dephosphorylating myosin so it can no longer interact with actin so causing relaxation.
  • Therefore the activation of these receptors both promotes contraction, while inhibiting relaxation
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5
Q

•Common side effects of salbutamol include?

A
  • Increased heart rate
  • Increased tremor
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6
Q

•In addition to asthma what other conditions can salbutamol be used to treat?

A

•Premature labour between 22 and 37 weeks of pregnancy-both oral and IV preparations can be used.

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