Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 75

Steady‐state hydration in the cornea occurs when the endothelial leak and pump rates are equivalent; this process is termed the “pump–leak” mechanism. The leaky barrier function of the endothelium may at first seem counterintuitive, but most nutrients for the cornea, except oxygen, come from the AH. Thus, leakiness of the endothelium is essential to providing bulk fluid flow through a tissue that lacks blood and lymphatic vessels. Glucose transporters are found on both the apical and basolateral endothelial cell membranes that face the AH and stroma, respectively, to ensure transcellular glucose flux. The corneal epithelium converts glucose to glucose 6‐phosphate, where it is subsequently metabolized to pyruvate via glycolysis. Most of this pyruvate is then metabolized into lactate, but some is diverted into the tricarboxylic acid cycle to produce ATP. Glucose is also stored in the epithelium as glycogen, which can be used for energy under stressful conditions such as corneal injury. The corneal epithelium and keratocytes in the anterior stroma obtain oxygen for aerobic glycolysis from the PTF, while the endothelium and keratocytes in the posterior stroma receive their oxygen from the AH.