Qadri Y H, Swamy A N, Rao J V
Toxicology Unit, Indian Institute of Chemical Technology, Hyderabad.
Ecotoxicol Environ Saf. 1994 Jun;28(1):91-8. doi: 10.1006/eesa.1994.1037.
Species-related differences in sensitivity to acute intoxication by anticholinesterase (anti-ChE) compounds have been attributed, in large part, to differences in the kinetics of inhibition of acetylcholinesterase (AChE: EC 3.1.1.7) in vitro. The following investigation was designed to determine if species-related differences in the sensitivity of brain AChE to inhibition by monocrotophos (MCP) could contribute to the interspecies differences in toxicity. Brain AChE activity was significantly greater in fish followed by pigeon and rat. MCP was found to be a competitive inhibitor of rat, pigeon, and fish brain AChE, thereby, altering the Km (Michaelis constant) widely among the species. Comparatively, least alterations in Km were observed in fish and maximum in pigeon. The Ki (bimolecular inhibition constant) of rat was 1.4- and 3.2-fold lower than that of pigeon and fish, respectively. Although fish brain had significantly greater AChE activity, it was the least sensitive to MCP inhibition. These data suggest that the greater sensitivity of rodent brain AChE to inhibition by MCP may contribute to the greater toxicity of MCP in rodents than in birds and fishes.
抗胆碱酯酶（anti-ChE）化合物急性中毒敏感性的物种差异，在很大程度上归因于体外乙酰胆碱酯酶（AChE：EC 3.1.1.7）抑制动力学的差异。以下研究旨在确定脑AChE对久效磷（MCP）抑制敏感性的物种差异是否会导致种间毒性差异。鱼脑中的AChE活性显著高于鸽子和大鼠。发现MCP是大鼠、鸽子和鱼脑AChE的竞争性抑制剂，因此，不同物种间的米氏常数（Km）变化很大。相比之下，鱼脑中Km的变化最小，鸽子中最大。大鼠的双分子抑制常数（Ki）分别比鸽子和鱼低1.4倍和3.2倍。虽然鱼脑的AChE活性显著更高，但它对MCP抑制的敏感性最低。这些数据表明，啮齿动物脑AChE对MCP抑制的更高敏感性可能导致MCP对啮齿动物的毒性高于鸟类和鱼类。
