A researcher wants to determine what controls smooth muscle contractility. Case
ID: 167968 • Letter: A
Question
A researcher wants to determine what controls smooth muscle contractility. Case 1. First, while keeping other factors constant, he added a drug that specifically activated the activities of Rho kinase. (a) What happened to the contractility of the cell? Why? Case 2. further testing, he separately added a different reagent that could inhibit the activity of m light chain kinase. (b) What happened to the cell contractility this time? Why? Case 3. Then he repeated the above in Case 1 when myosin light chain kinase activities were either increased or decreased (c) Speculate the contractile the smooth muscle cell.Explanation / Answer
Smooth Muscle Contraction Mechanism:
Ca2+
Calmodulin Ca-Calmodulin
Inactive Myosin Light Chain Kinase Active Myosin Light Chain Kinase
Myosin Light chains Phosphorylation of Myosin light chains
Actin + Myosin Actomyosin Contraction
Rho Kinase involved in the de phosphorylation of Myosin light chains, there by helps in smooth muscle relaxation.
Now we will answer the below questions:
A researcher wants to determine what controls smooth muscle contractility.
Case l. First, while keeping other factors constant. he added a drug that specifically activated the activities of Rho kinase.
(a) What happened to the contractility of the cell?
Answer: Smooth muscle relaxes, because Rho Kinase involved in the de phosphorylation of Myosin light chains.
Case 2. To do further testing, he separately added a different reagent that could inhibit the activity of myosin light chain kinase.
(b) What happened to the cell contractility this time? Why?
Answer: Cell contraction will not happen, since myosin light chain kinase activity is inhibited.
Case 3. Then he repeated the above experiments in Case I when myosin light chain kinase activities were either increased or decreased.
(c) Speculate the contractile state of the smooth muscle cell.
Answer: Irrespective of MLCK activity, smooth muscle undergo relaxation hence Rho kinase dephosphorylates the myosin light chains there by, inhibits the further steps leading to contraction.