Venza I, Valenti A, Ruggeri P, Denaro L, Teti D
Institute of General Pathology, Faculty of Medicine and Surgery, University of Messina, Italy.
Physiol Res. 2000;49(2):207-12.
The retina is characterized by glycolysis under aerobic conditions, mediated by lactate dehydrogenase isoenzyme-5 (LDH-5) as well as by the soluble isoenzyme of malate dehydrogenase. Bovine retina LDH and MDH isoenzymes and their activities were studied after polyamine treatment. Our results showed that LDH-5 isoenzyme presented the highest activity in untreated as well as in putrescine-treated retina. Decreased activity was present when the retina was treated with spermidine or spermine. It was demonstrated that retinic LDH-5 had a high affinity for lactate which enabled the isoenzyme to be more effective than the other LDH isoenzymes in the conversion of NADH to NAD. Therefore, the putrescine enhancing LDH-5 activity appeared to be capable of stimulating NAD-mediated rhodopsin regeneration. Putrescine induced a marked increase of both MDH isoenzymes--soluble (s-MDH) and mitochondrial (m-MDH), while spermine and spermidine mostly affected the soluble form of the enzyme. Putrescine induced a three-fold increase in s-MDH and m-MDH activities, while spermine and spermidine induced a four to five-fold increase in s-MDH. These results document the differential effects of polyamine treatment on LDH and MDH isoenzyme activities.
视网膜的特征是在有氧条件下进行糖酵解，由乳酸脱氢酶同工酶-5（LDH-5）以及苹果酸脱氢酶的可溶性同工酶介导。在进行多胺处理后，对牛视网膜的LDH和MDH同工酶及其活性进行了研究。我们的结果表明，LDH-5同工酶在未处理的视网膜以及用腐胺处理的视网膜中活性最高。当视网膜用亚精胺或精胺处理时，活性降低。结果表明，视网膜中的LDH-5对乳酸具有高亲和力，这使得该同工酶在将NADH转化为NAD的过程中比其他LDH同工酶更有效。因此，腐胺增强LDH-5活性似乎能够刺激NAD介导的视紫红质再生。腐胺可使两种MDH同工酶——可溶性（s-MDH）和线粒体（m-MDH）均显著增加，而亚精胺和精胺主要影响该酶的可溶性形式。腐胺可使s-MDH和m-MDH活性增加三倍，而亚精胺和精胺可使s-MDH活性增加四至五倍。这些结果证明了多胺处理对LDH和MDH同工酶活性的不同影响。
