Ionic exchange in the corneal endothelium depends upon the metabolic rate. Which of the following can block Ionic exchange in corneal endothelium?
Correct Answer: Inhibition of anaerobic glycolysis
Description: A i.e. Inhibition of anaerobic glycolysis Endothelium provides a leaky barrier to aqueous humor by allowing molecules & electrolytes of small size (2-3nm) to penetrate through focal tight junctions (maculae occludentes). This barrier function is Ca" dependent. The delicate balance between fluid entering corneal stroma (barrier function) and fluid egressing (4-5 Ju1/cm2/hour) the stroma (Na+ K+ ATPase pump function) maintain the corneal hydration at a fixed level of 78%. Any change would cause corneal oedema. Corneal stroma contains glycosaminoglycans (GAG) which is the main cause of corneal hydration and swelling pressure (50mmHg). GAG has anionic charges 1/t separation of one molecule from other making it a sponge like structure that can swell & get hydrated The GAG anionic repulsion expands the tissue and sucks in fluid with equal pressure called imbibation pressure (-30 mmHg) Intraocular pressure (20) = Swelling pressure (50) + Imbibation pressure (-30) Corneal oedema occurs if IOP exceeds SP as in glaucoma or if SP is low (with normal 10P) as in endothelial dystrophy. Endothelial pump is dependent on presence of Cl- & HCO3- and can be slowed down by carbonic anhydrase inhibitor. Basolateral Na+/2HCO3 cotranspo, Na+/KV2C1- cotranspo, C1-/HCO3- exchange, apical anion channels permeable to both Cl- & HCO3- and carbonic anhydrase mediated CO2 diffusion mode of apical HCO3 flux are various anion transpo mechanisms in endothelium. When ATP produced by both glycolysis and aerobic respiration was inhibited by 0.1 mmol/l iodoacetamide, the endothelial cells could not survive but when ATP synthesis alone by aerobic respiration was inhibited by 1.0 mmol/L KCN, the endothelial cells survived for at least 1 week on the ATP produced by anaerobic glycolysisQ.
Category:
Ophthalmology
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