Suchail S, Guez D, Belzunces L P
INRA, Laboratoire de Toxicologie Environnementale, UMR INRA-UAPV Ecologie des Invertébrés, Avignon, France.
Environ Toxicol Chem. 2001 Nov;20(11):2482-6. doi: 10.1897/1551-5028(2001)020<2482:dbaact>2.0.co;2.
Imidacloprid is a systemic nitroguanidine insecticide that belongs to the neonicotinoid family. As an agonist of the acetylcholine receptor, it attacks the insect nervous system and is extremely effective against various sucking and mining pests. Oral acute and chronic toxicity of imidacloprid and its main metabolites (5-hydroxyimidacloprid, 4,5-dihydroxyimidacloprid, desnitroimidacloprid, 6-chloronicotinic acid, olefin, and urea derivative) were investigated in Apis mellifera. Acute intoxication by imidacloprid or its metabolites resulted in the rapid appearance of neurotoxicity symptoms, such as hyperresponsiveness, hyperactivity, and trembling and led to hyporesponsiveness and hypoactivity. For acute toxicity tests, bees were treated with doses of toxic compounds ranging from 1 to 1,000 ng/bee (10-10,000 microg/kg). Acute toxicity (LD50) values of imidacloprid were about 60 ng/bee (600 microg/kg) at 48 h and about 40 ng/bee (400 microg/kg) at 72 and 96 h. Out of the six imidacloprid metabolites tested, only two (5-hydroxyimidacloprid and olefin) exhibited a toxicity close to that of imidacloprid. Olefin LD50 values were lower than those of imidacloprid. The 5-hydroxyimidacloprid showed a lower toxicity than imidacloprid with a LD50 four to six times higher than that of imidacloprid. Urea also appeared as a compound of nonnegligible toxicity by eliciting close to 40% mortality at 1,000 ng/bee (10,000 microg/kg). However, no significant toxicity was observed with 4,5-dihydroxyimidacloprid, 6-chloronicotinic acid, and desnitroimidacloprid in the range of doses tested. To test chronic toxicity, worker bees were fed sucrose solutions containing 0.1, 1, and 10 microg/L of imidacloprid and its metabolites for 10 d. Fifty percent mortality was reached at approximately 8 d. Hence, considering that sucrose syrup was consumed at the mean rate of 12 microl/d and per bee, after an 8-d period the cumulated doses were approximately 0.01, 0.1, and 1 ng/bee (0.1, 1, and 10 microg/kg). Thus, all tested compounds were toxic at doses 30 to 3,000 (olefin), 60 to 6,000 (imidacloprid), 200 to 20,000 (5-OH-imidacloprid), and >1,000 to 100,000 (remaining metabolites) times lower than those required to produce the same effect in acute intoxication studies. For all products tested, bee mortality was induced only 72 h after the onset of intoxication.
吡虫啉是一种内吸性硝基胍类杀虫剂，属于新烟碱类。作为乙酰胆碱受体激动剂，它作用于昆虫神经系统，对各类刺吸式和蛀食性害虫极为有效。研究了吡虫啉及其主要代谢产物（5-羟基吡虫啉、4,5-二羟基吡虫啉、去硝基吡虫啉、6-氯烟酸、烯烃和尿素衍生物）对意大利蜜蜂的经口急性和慢性毒性。吡虫啉或其代谢产物急性中毒会迅速出现神经毒性症状，如反应过度、活动亢进和颤抖，进而导致反应迟钝和活动减少。急性毒性试验中，给蜜蜂施以剂量范围为1至1000纳克/只（10 - 10000微克/千克）的有毒化合物。吡虫啉的急性毒性（半数致死剂量，LD50）在48小时时约为60纳克/只（600微克/千克），72小时和96小时时约为40纳克/只（400微克/千克）。在所测试的六种吡虫啉代谢产物中，只有两种（5-羟基吡虫啉和烯烃）表现出与吡虫啉相近的毒性。烯烃的LD50值低于吡虫啉。5-羟基吡虫啉的毒性低于吡虫啉，其LD50比吡虫啉高4至6倍。在剂量为1000纳克/只（10000微克/千克）时，尿素也表现出不可忽视的毒性，导致近40%的死亡率。然而，在测试剂量范围内，4,5-二羟基吡虫啉、6-氯烟酸和去硝基吡虫啉未观察到明显毒性。为测试慢性毒性，给工蜂喂食含0.1、1和10微克/升吡虫啉及其代谢产物的蔗糖溶液，持续10天。约8天时达到50%死亡率。因此，考虑到每只蜜蜂平均每天消耗12微升蔗糖糖浆，8天后累积剂量约为0.01、0.1和1纳克/只（0.1、1和10微克/千克）。所以，所有测试化合物产生相同效果的剂量比急性中毒研究中的剂量低30至3000倍（烯烃）、60至6000倍（吡虫啉）、200至20000倍（5-羟基吡虫啉）以及>1000至100000倍（其余代谢产物）。对于所有测试产品，蜜蜂在中毒开始后仅72小时出现死亡。
