13- AH composition and production notes

What does ultrafiltration due?

produces a reservoir of fluid in stroma of cilairy processes

When is ultrafiltrate produced?

only when the net hydrostatic pressure is greater than oncotic pressure

What makes up the net hydrostatic pressure?

hydrostatic pressure of capillaries - IOP (stromal pressure)

What is ciliary process secretion?

movement of ions into anterior chamber via ciliary epithelium

Ultrafiltration vs ciliary process secretion (IOP?)

Ultrafilatrate: dependent on IOP

secretion: IOP independent

Ciliary epithelium transport of ions pathway

1. High Na+ in stroma

2. Na+ gradient drives NKCC, 1Na+, 1K+, 2Cl- into pigmented epithelium

3. Na+ gradient drives NHE, 1Na+ into cell and 1H+ out of cell (PE)

4. Carbonic anhydrase converts CO2 into HCO3- + H+

5. AE uses HCO3- gradient to bring HCO#- out of cell and Cl into cell (PE)

6. Build up of Cl- + Na+ in cell (PE) draws water in via aquaporins

7. Na+ + Cl- move into NPE via gap junctions

8. NKA on NPE brings 3Na+ out of cell + into posterior chamber + 2K+ into cell (NPE)

9. AE uses HCO3- gradient to send HCO3- into posterior chamber + Cl- into cell (NPE)

10. CaCC sends Cl- into posterior chamber

11. High ion concentration in posterior chamber draws H2O out of NPE + into post chamber via aquaporins

Ciliary epithelium transport of glucose uses what?

sodium dependent glucose transporters (SGLT)

glucose transporters (GLUT)

Where are SGLTs located?

pigmented epithelium (facing stroma)

Where are GLUTs located?

nonpigemented epi (faces posterior chamber)

Ciliary epithelium transport of ascorbate uses what?

sodium vitamin C transporter (SVCT)

What does SVCT need to work?

Na+ gradient and ATP

Where are SVCTs located?

on pigmented epi only (facing stroma)

What does ascorbate do?

absorbs UVA + UVB light

donates e- to ROS stabilizing it

What does urea do?

absorbs UVA + UVB light

donates e- to ROS stabilizing it

How is AH production regulated?

sympathetic nervous sytem via B receptors

adenosine

How does binding to beta receptors trigger AH production?

triggers formation of cAMP, which activates Cl- channels

activate NKCC

How does adenosine trigger AH production?

binds to A3 receptors, which make cAMP, stimulating Cl- channels

Ciliary blood vessels/epithelium have what nerves on it?

both sympathetic + parasympathetic nerves

What is timolol + what does it do?

nonselective Beta blocker

decreases AH production + IOP

What is isoprotenol + what does it do?

Beta agonist

increases AH production + IOP

What does dorzolamide/brinzolamide do?

inhibits carbonic anhydrase, decreasing HCO3-, decreasing Cl-, decreases AH + IOP

What is clonidine and what does it do + what is its MOA?

alpha-2 agonist, decreases AH + IOP

inhibits presynaptic sympathetic nerves and vasodilates blood vessels

What does aproclondidne do? How?

inhibits NPE secretion

reduces cAMP, which decreases Ca2+ therefore decreasing Cl- channel activity

When is AH production affected by IOP?

only when it is very high

What happens to IOP at night?

IOP increases

What happens to AH production at night?

decreases

Why do beta blockers like timolol not decrease IOP at night?

Because the block AH production, but AH production is already reduced at night, IOP is due to something else

What is aniridia and what causes is?

congenital lack of iris due to mutation in Pax6 genes

What problems does aniridia cause?

CB development (+lens + chamber angle)

high risk for developing glaucoma

When does the CB + iris develop?

after lens, optic vesicle, and corneal formation

What parts of CB (epi, muscle, vasculature) are derived from what?

epithelium: ectoderm

muscle: ectoderm (neural crest)

vasculature: mesoderm

What parts of iris (epi, stroma, vasculature) are derived from what?

epithelium: ectoderm

stroma: ectoderm (neural crest)

vasculature: mesoderm

What is TM derived from?

ectoderm (neural crest)

What is schelmms canal derived from?

mesoderm

What is iris coloboma due to?

ventral optic fissure not fusing properly

What does iris coloboma cause?

disrupts CB development in same area that iris is missing

What is the difference in contents between AH + plasma ?

1. AH has much less proteins (for transparency)

2. AH has more ascorbate

3. AH has more lactate

4. AH has lower pH than blood

What are the major ions of AH?

1. Na+, Cl-

2. HCO3-, lactate

What are the organic molecules of AH?

ascorbate

urea

glucose

lactate

What is normal level of AH production?

2.5 microliters/min

AH + blood flow relationship

1. if blood flow is normal - 75% below normal, ultrafiltrate/AH production is independent of blood flow

3. if blood flow is more than 75% below normal, AH production/ultrafiltrate is decreased

How does age affect AH production?

decreases with age

Why does IOP not change with age in AH production decreases?

because AH drainage also decreases with age