Almeida-Val V M, Farias I P, Silva M N, Duncan W P, Val A L
Instituto Nacional de Pesquisas da Amazônia, Manaus, Brasil.
Braz J Med Biol Res. 1995 Nov-Dec;28(11-12):1257-63.
The isozyme distribution of cichlid lactate dehydrogenase (LDH) is related to species environmental preferences. Cichlasoma amazonarum occurs in different environments and presents LDH tissue distribution patterns that correlate with oxygen tension at the capture location. Cichlasoma amazonarum was exposed to long-term severe hypoxia (51 days at 36.4 +/- 5.9 mmHg), tissue LDH isozyme distribution was analyzed by electrophoresis and enzyme activities were measured by monitoring the oxidation of NADH as pyruvate was reduced to lactate. The exposure of Cichlasoma amazonarum to long-term severe hypoxia resulted in changes in the tissue distribution of LDH isozymes. The major changes in response to hypoxia occurred in heart, liver and brain: isozyme A4 was activated in heart and brain, whereas isozyme B4 was activated in liver. The most significant quantitative change occurred in brain LDH of hypoxia-exposed animals which adopted muscle type kinetics, reflecting a new LDH isozyme distribution. LDH activity was significantly reduced (P < 0.05) in animals exposed to hypoxia (N = 8), suggesting an overall LDH suppression. Pyruvate inhibition decreased in all hypoxia-exposed tissues. Thus, the ability of Cichlasoma amazonarum to regulate LDH tissue expression according to oxygen availability allows the animal to survive chronic hypoxic environments. This phenotypic plasticity may occur in other hypoxia-tolerant fish species.
丽鱼科乳酸脱氢酶（LDH）的同工酶分布与物种的环境偏好有关。亚马逊丽体鱼生活在不同环境中，其LDH组织分布模式与捕获地点的氧张力相关。将亚马逊丽体鱼暴露于长期严重缺氧环境（在36.4±5.9 mmHg下51天），通过电泳分析组织LDH同工酶分布，并在丙酮酸还原为乳酸时通过监测NADH的氧化来测量酶活性。亚马逊丽体鱼长期暴露于严重缺氧环境导致LDH同工酶的组织分布发生变化。对缺氧的主要反应变化发生在心脏、肝脏和大脑：同工酶A4在心脏和大脑中被激活，而同工酶B4在肝脏中被激活。暴露于缺氧环境的动物大脑LDH发生了最显著的定量变化，其采用肌肉型动力学，反映了一种新的LDH同工酶分布。暴露于缺氧环境的动物（N = 8）的LDH活性显著降低（P < 0.05），表明总体上LDH受到抑制。所有暴露于缺氧环境的组织中丙酮酸抑制作用均降低。因此，亚马逊丽体鱼根据氧可用性调节LDH组织表达的能力使该动物能够在慢性缺氧环境中生存。这种表型可塑性可能也存在于其他耐缺氧鱼类物种中。
