Fliesler S J, Richards M J, Miller C Y, Mckay S, Winkler B S
Saint Louis University Eye Institute, Saint Louis University, School of Medicine, MO 63104, USA.
Exp Eye Res. 1997 May;64(5):683-92. doi: 10.1006/exer.1996.0281.
The metabolic competence and histological integrity of the frog retina in vitro were evaluated as a function of the presence/absence of exogenous glucose and of oxygen tension. Dark- and light-adapted frog neural retinas were incubated for 1-8 hr at 23 degrees C in a modified Ringer's-bicarbonate medium under aerobic and anaerobic conditions, in the presence and absence of 10 mM glucose. Control retinas (+glucose, aerobic conditions) maintained ATP levels comparable to those of freshly excised tissue (ave. 17 nmol mg protein-1), produced minimal lactate (ave. 0.12 mumol mg protein-1 hr-1), and exhibited normal histology. In the absence of any exogenous carbon source, retinas incubated aerobically maintained ATP levels, produced lactate, incorporated [3H]acetate into nonsaponifiable lipids, and exhibited histology comparable to controls. In the presence of 1 mM iodoacetate, aerobic ATP levels declined markedly, with or without exogenous glucose. Under anaerobic conditions with glucose present, lactate production increased ca. 8.5-fold, while ATP levels were maintained at control levels, demonstrating a marked Pasteur effect; under these conditions, retinas exhibited only moderate histopathological changes. However, in the absence of both glucose and oxygen, ATP levels declined precipitously, with concomitant massive cytological deterioration. No major differences in the biochemical measurements or histological appearance were observed as a function of light adaptation. These results demonstrate the remarkable resilience of the frog retina to anoxia and hypoglycemic stress. Aerobically, with or without exogenous glucose, ATP production and de novo lipid synthesis are maintained, apparently by recruitment of an endogenous carbohydrate substrate (e.g., glycogen).
根据外源葡萄糖的有无以及氧张力，对体外培养的青蛙视网膜的代谢能力和组织学完整性进行了评估。将暗适应和光适应的青蛙神经视网膜在23℃下于改良的林格氏碳酸氢盐培养基中，在有氧和无氧条件下，分别在有和没有10 mM葡萄糖的情况下孵育1 - 8小时。对照视网膜（+葡萄糖，有氧条件）维持的ATP水平与新鲜切除的组织相当（平均17 nmol mg蛋白质-1），产生的乳酸极少（平均0.12 μmol mg蛋白质-1小时-1），并且组织学正常。在没有任何外源碳源的情况下，有氧孵育的视网膜维持ATP水平，产生乳酸，将[3H]乙酸盐掺入非皂化脂质中，并且组织学与对照相当。在存在1 mM碘乙酸的情况下，无论有无外源葡萄糖，有氧ATP水平均显著下降。在有葡萄糖存在的厌氧条件下，乳酸产生增加约8.5倍，而ATP水平维持在对照水平，显示出明显的巴斯德效应；在这些条件下，视网膜仅表现出中度的组织病理学变化。然而，在没有葡萄糖和氧气的情况下，ATP水平急剧下降，同时伴随着大量的细胞学恶化。未观察到生化测量或组织学外观因光适应而有重大差异。这些结果表明青蛙视网膜对缺氧和低血糖应激具有显著的恢复能力。在有氧条件下，无论有无外源葡萄糖，ATP产生和从头脂质合成均得以维持，显然是通过募集内源性碳水化合物底物（如糖原）实现的。
