Sokolova I M
Biology Department, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte NC 28223, USA.
J Exp Biol. 2004 Jul;207(Pt 15):2639-48. doi: 10.1242/jeb.01054.
Marine intertidal mollusks, such as oysters, are exposed to multiple stressors in estuaries, including varying environmental temperature and levels of trace metals, which may interactively affect their physiology. In order to understand the combined effects of cadmium and elevated temperature on mitochondrial bioenergetics of marine mollusks, respiration rates and mitochondrial volume changes were studied in response to different cadmium levels (0-1000 micromol l(-1)) and temperatures (15, 25 and 35 degrees C) in isolated mitochondria from the eastern oyster Crassostrea virginica acclimated at 15 degrees C. It was found that both cadmium and temperature significantly affect mitochondrial function in oysters. Elevated temperature had a rate-enhancing effect on state 3 (ADP-stimulated) and states 4 and 4+ (representative of proton leak) respiration, and the rate of temperature-dependent increase was higher for states 4 and 4+ than for state 3 respiration. Exposure of oyster mitochondria to 35 degrees C resulted in a decreased respiratory control and phosphorylation efficiency (P/O ratio) compared to that of the acclimation temperature (15 degrees C), while an intermediate temperature (25 degrees C) had no effect. Cadmium exposure did not lead to a significant volume change in oyster mitochondria in vitro. Low levels of cadmium (1-5 micromol l(-1)) stimulated the rate of proton leak in oyster mitochondria, while not affecting ADP-stimulated state 3 respiration. In contrast, higher cadmium levels (10-50 micromol l(-1)) had little or no effect on proton leak, but significantly inhibited state 3 respiration by 40-80% of the control rates. Elevated temperature increased sensitivity of oyster mitochondria to cadmium leading to an early inhibition of ADP-stimulated respiration and an onset of complete mitochondrial uncoupling at progressively lower cadmium concentrations with increasing temperature. Enhancement of cadmium effects by elevated temperatures suggests that oyster populations subjected to elevated temperatures due to seasonal warming or global climate change may become more susceptible to trace metal pollution, and vice versa.
海洋潮间带软体动物，如牡蛎，在河口会受到多种应激源的影响，包括环境温度变化和痕量金属水平，这些因素可能会相互作用影响它们的生理机能。为了了解镉和温度升高对海洋软体动物线粒体生物能量学的综合影响，研究了来自在15℃驯化的美国牡蛎（Crassostrea virginica）的分离线粒体对不同镉水平（0 - 1000微摩尔/升）和温度（15、25和35℃）的呼吸速率和线粒体体积变化。结果发现，镉和温度都显著影响牡蛎的线粒体功能。温度升高对状态3（ADP刺激的）以及状态4和4 +（代表质子泄漏）呼吸有速率增强作用，并且状态4和4 +的温度依赖性增加速率高于状态3呼吸。与驯化温度（15℃）相比，将牡蛎线粒体暴露于35℃会导致呼吸控制和磷酸化效率（P/O比）降低，而中间温度（25℃）则没有影响。在体外，镉暴露不会导致牡蛎线粒体体积发生显著变化。低水平的镉（1 - 5微摩尔/升）刺激了牡蛎线粒体中的质子泄漏速率，同时不影响ADP刺激的状态3呼吸。相反，较高的镉水平（10 - 50微摩尔/升）对质子泄漏几乎没有影响，但显著抑制状态3呼吸，抑制程度为对照速率的40 - 80%。温度升高增加了牡蛎线粒体对镉的敏感性，导致ADP刺激的呼吸早期受到抑制，并且随着温度升高，在逐渐降低的镉浓度下开始完全线粒体解偶联。温度升高增强镉的影响表明，由于季节性变暖或全球气候变化而经历温度升高 的牡蛎种群可能更容易受到痕量金属污染的影响，反之亦然。
