Ip Yuen K, Kuah Sharon S L, Chew Shit F
Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore.
Physiol Biochem Zool. 2004 Sep-Oct;77(5):824-37. doi: 10.1086/423746.
The effects of sulfide on the energy metabolism of Boleophthalmus boddaerti in normoxia and hypoxia were examined. The 24-, 48-, and 96-h LC50 values of sulfide for B. boddaerti with body weight ranging from 11.6 to 14.2 g were 0.786, 0.567, and 0.467 mM, respectively. The tolerance of B. boddaerti to sulfide was not due to the presence of a sulfide-insensitive cytochrome c oxidase. There was no accumulation of lactate in the muscle and liver of specimens exposed to sulfide in normoxia. In addition, the levels of ATP, AMP, and energy charge in both the muscle and the liver were unaffected. These results indicate that B. boddaerti was able to sustain the energy supply required for its metabolic needs via mainly aerobic respiration when exposed to sulfide (up to 0.4 mM) in normoxia. Exposure of B. boddaerti simultaneously to hypoxia and 0.2 mM sulfide for 48 h resulted in decreases in the ATP levels in the muscle and liver. However, the energy charge in both tissues remained unchanged, and the level of lactate accumulated in the muscle was too low to have any major contribution to the energy budget of the fish. Our results reveal that B. boddaerti possesses inducible mechanisms to detoxify sulfide in an ample supply or a lack of O2. In normoxia, it detoxified sulfide to sulfate, sulfite, and thiosulfate. There were significant increases in the activities of sulfide oxidase in the muscle and liver of specimens exposed to sulfide, with that in the liver being >13-fold higher than that in the muscle. However, in hypoxia, sulfide oxidase activity in the liver was suppressed in response to environmental sulfide. In such conditions, there were significant increases in the activities of sulfane sulfur-forming enzyme(s) in the muscle and liver that were not observed in specimens exposed to sulfide in normoxia. Correspondingly, there were no changes in the levels of sulfate or sulfite in the muscle or liver. Instead, B. boddaerti detoxified sulfide mainly to sulfane sulfur in hypoxia. In conclusion, B. boddaerti was able to activate different mechanisms to detoxify sulfide, producing different types of detoxification products in normoxia and hypoxia.
研究了硫化物对弹涂鱼在常氧和低氧条件下能量代谢的影响。体重在11.6至14.2克之间的弹涂鱼，硫化物的24小时、48小时和96小时半数致死浓度（LC50）分别为0.786毫摩尔、0.567毫摩尔和0.467毫摩尔。弹涂鱼对硫化物的耐受性并非由于存在对硫化物不敏感的细胞色素c氧化酶。在常氧条件下暴露于硫化物的标本的肌肉和肝脏中没有乳酸积累。此外，肌肉和肝脏中的三磷酸腺苷（ATP）、一磷酸腺苷（AMP）水平以及能荷均未受影响。这些结果表明，在常氧条件下，当暴露于硫化物（高达0.4毫摩尔）时，弹涂鱼能够主要通过有氧呼吸维持其代谢需求所需的能量供应。将弹涂鱼同时暴露于低氧和0.2毫摩尔硫化物环境中48小时，导致肌肉和肝脏中的ATP水平下降。然而，两个组织中的能荷保持不变，并且肌肉中积累的乳酸水平过低，对鱼的能量收支没有任何重大贡献。我们的研究结果表明，弹涂鱼具有可诱导的机制，在硫化物供应充足或缺乏氧气的情况下对硫化物进行解毒。在常氧条件下，它将硫化物解毒为硫酸盐、亚硫酸盐和硫代硫酸盐。暴露于硫化物的标本的肌肉和肝脏中，硫化物氧化酶的活性显著增加，肝脏中的活性比肌肉中的高13倍以上。然而，在低氧条件下，肝脏中的硫化物氧化酶活性因环境中的硫化物而受到抑制。在这种情况下，肌肉和肝脏中形成硫烷硫的酶的活性显著增加，而在常氧条件下暴露于硫化物的标本中未观察到这种情况。相应地，肌肉或肝脏中的硫酸盐或亚硫酸盐水平没有变化。相反，在低氧条件下，弹涂鱼主要将硫化物解毒为硫烷硫。总之，弹涂鱼能够激活不同的机制对硫化物进行解毒，在常氧和低氧条件下产生不同类型的解毒产物。
