Lecture 2

Question 1

What is the structure of the airway surface liquid?

Answer 1

ASL sits on top of epithelial cells of the respiratory tract
Periciliary layer sit on top of epithelia
Cilia project from cells into PCL Cilia are motile and beat constantly – move liquid layer as well as the mucous layer which sits on top up the respiratory tract

Question 2

Which direction does the ASL move?

what’s the structure?

Answer 2

proximal to distal
proximal - small airways 2m2
Small airways converge in bronchial region – 50 cm2
Height gets bigger because the surface area gets smaller
Distal – upper respiratory tract

Question 3

Whats the difference between the 2 ways of controlling ASL?

Answer 3

• Passive:
o Mucous layer acts as a reservoir
o If height of PCL gets too high excess fluid moves into mucous layer.
• Active:
o Active ion transport controlling salt level in PCL – ENaC and CFTR
o Active transport of ions and therefore water in and out of PCL
o More important – determines height
o ENaC and CFTR – complementary

Question 4

What is the optimum height of ASL?

Answer 4

7-7.5um is optimum height

Question 5

How are the different ions involved in regulating the height?

Answer 5

Na+ absorption – enhanced If too height
Move Na out, water will follow – height goes down.
Cl- secretion dominates at a steady state
Balance between Cl secretion and Na absorption so no net water movement.

Question 6

Role of amiloride

Answer 6

Amiloride blocks ENaC - can be used to see regulation via epithelial Na channels.

Question 7

Role of bumetanide

Answer 7

Bumetanide blocks NKCC1 – when blocked it stops chloride secretion – looks at contribution of CFTR

Question 8

Role of forskolin

Answer 8

stimulates CFTR - Cl secretion

Question 9

How do you measure murine nasal PDs?

Answer 9

•Measured transepithelial potential across the nasal epithelium
oReference electrode and recording electrode in nose of anaesthetised mice.