Salbutamol Practical Class Flashcards
1
Q
Complete the diagram on the mechanism of action
A
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.
3
Q
Complete the diagram
A
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
5
Q
•Common side effects of salbutamol include?
A
- Increased heart rate
- Increased tremor
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.