Müller Glia Physiology (F) Flashcards
What cover virtually all the capillary walls in the retina to provide structural and metabolic support to retinal neurons and the inner blood–retinal barrier?
end-feet of Müller cells
What do Muller cells secrete that enhance barrier function of endothelial cells?
Thrombospondin-1 and GDNF
What do Muller cells store for the use of energy?
glycogen
What do Muller cells convert glucose into?
lactate
What are the functions that lactate can have in the eye?
- Lactate dehydrogenase converts lactate back to pyruvate for use in oxidative phosphorylation in photoreceptors
- mediates vasodilation of retinal capillaries
What do Muller cells produce that will cause an increase in vascular permeability and metalloproteinase (MMP) expression which breaks down tight junctions? 1. When does it release this? 2
- VEGF
2. hypoxic conditions
What is thought to be the reason why neovasculature occurs toward vitreous and not within retina during diabetic retinopathy?
Muller cells also provide an anti-proliferative effect of endothelial cells by secreting anti-angiogenic factors
What is thought to be the reason why neovasculature occurs toward vitreous and not within retina during diabetic retinopathy?
Muller cells also provide an anti-proliferative effect of endothelial cells by secreting anti-angiogenic factors
What are the functions of glutamate uptake in Muller cells?
- Prevents lateral spread of glutamate signal to neighboring synapses
- Modifies the synaptic response
- Prevents glutamate induced neurotoxicity
What transports glutamate into Muller cells? 1. What is imported and exported? 2
- GLAST
2. Brings in 3 Na+, 1 H+, and 1 Glutamate anion in exchange for 1 K+ ion
What is used to convert glutamate into glutamine?
glutamine synthase, ATP, and NH4+
What is used and what is the byproduct of turning glutamine into glutamate? 1. Where does this take place? 2
- Use glutaminase and NH4+ is byproduct
2. bipolar cells
What is used and what is the byproduct of turning glutamine into glutamate? 1. Where does this take place? 2
- Use glutaminase and NH4+ is byproduct
2. bipolar cells
What is a glutamate-cysteine-glycine tripeptide that scavenges free radicals?
glutathione
In the retina under normal conditions, where is glutathione confined to?
Müller cells, astrocytes, and horizontal cells
In the retina under normal conditions, where is glutathione confined to?
Müller cells, astrocytes, and horizontal cells
What is the major inhibitory neurotransmitter in the vertebrate retina? 1. How is termination of this NT achieved? 2
- GABA
2. uptake into presynaptic neuronal terminals and surrounding Müller cells through GAT
What goes into and out of the cell from GAT?
GABA, 2 Na+, and Cl- in
How is extracellular K+ regulated?
potassium inward rectifying channels located in Müller cell membranes (Kir4.1)
What happens to the amount of Kir4.1 channels with age? 1. What is a congenital mutation in Kir4.1 gene that results in reduced retinal sensitivity due to altered K+ flux? 2
- decreases
2. EAST syndrome
What is expressed in Müller cells and is thought to mediate water transport in response to local ionic changes?
AQP4 (aquaporin)
What do Müller cells secrete upon VEGF signaling or glutamate uptake? 1. What is the purpose of this? 2
- ATP and adenosine
2. Prevents osmotic swelling of Muller cells
What is an essential and retinally abundant amino acid-like molecule (more abundant than all other free-amino acids) that functions as an antioxidant and osmolyte? 1. Where is this found? 2
- Taurine
2. Muller cells
Where is retinal Carbonic anhydrase II found? 1. Where is membrane bound Carbonic anhydrase XIV found? 2
- Muller and amacrine cells
2. retinal glial cells (found on extracellular surface)
Where is retinal Carbonic anhydrase II found? 1. Where is membrane bound Carbonic anhydrase XIV found? 2
- Muller and amacrine cells
2. retinal glial cells (found on extracellular surface)
Upon light stimulation what happens to the pH in the retina? 1. What do Muller cells do to help prevent over-excitation? 2
- alkalinization
2. Bicarbonate is effectively taken up by Muller cells but the protons are not which decreases the pH
What can happen to light collected at the Muller cell end foot in the inner portion of the retina
- directed toward photoreceptors
2. funneled to increase photoreceptor sensitivity
