地克珠利主要抑制柔嫩艾美耳球虫厌氧阶段虫体，但机制还不清楚。乳酸脱氢酶（LDH）是无氧糖酵解途径中末端酶，与球虫的生存密切相关。前期研究发现，柔嫩艾美耳球虫LDH仅在厌氧阶段虫体中高效表达，在地克珠利耐药株中表达量明显上调。我们推测地克珠利是抑制了球虫LDH酶活性，无法再生NAD+，糖酵解途径被终止，能量供给受阻而引发球虫发生死亡。本项目以柔嫩艾美耳球虫敏感株和地克珠利耐药株为研究对象，通过研究两个虫株的LDH基因及其靶标蛋白特性差异；药物对重组EtLDH酶活性作用，以及对需氧与厌氧阶段虫体LDH、NADH和NAD+影响的差异；将球虫LDH转染至酵母细胞以验证LDH与地克珠利之间关系；用流式细胞仪技术检测NAD+、ATP对药物处理后球虫子孢子和裂殖子入侵活力的影响，以探讨EtLDH在地克珠利抗柔嫩艾美耳球虫作用中扮演的角色。结果对阐明地克珠利抗球虫的分子机制及筛选新的药物靶标具有重要意义。

The diclazuril can inhibit effectively the the anaerobic stage of Eimeria tenella (schizogony and gametogony), however, little effect was found to the aerobic stage (sporogony). Previous studies had shown that the mRNA transcriptional level of E. tenella lactate dehydrogenase (EtLDH) was only observed in the intracellular stage (the schizont and meronts stage). The mRNA level of EtLDH was found to be significantly higher in the diclazuril-resistant strain in comparison with the drug-sensitive strain. Diclazuril had no effect on the diclazuril-resistant strain of Eimeria, but it can kill effectively the drug-sensitive strain, suggested that LDH plays an important role in the mechanism of diclazuril against E. tenalla..Lactate dehydrogenase, the last enzyme of the anaerobic glycolytic pathway, can catalyze NADH to deoxygenate the pyruvate into lactic acid while releasing of the NAD+. This NAD+ was utilized by glyceraldehyde 3-phosphate, the next round of the glycolytic cycle was proceeded and the ATP was provided to the parasites. Therefore, we speculated that the mechanism of diclazuril against E. tenalla was: the activity of E. tenella LDH was inhibited by diclazuril, which could not catalyze NADH to deoxygenate the pyruvate into lactic acid. The NAD+ was not generated and no NAD+ could be utilized by the glyceraldehyde 3-phosphate which caused the stop of next round of glycolysis pathway. The ATP could not be produced and the energy supply was ended which lead to the parasites dead. .The purpose of this project is to investigate the potential role of lactic dehydrogenase in the mechanism of diclazuril against E. tenalla with the following works: 1)Comparison the differences of EtLDH gene and its target proteins between the E. tenella drug-sensitive strain and diclazuril- resistant strain; 2)Effect of diclazuril on the recombinant EtLDH from the drug-sensitive strain and diclazuril- resistant strain; 3)Effect of diclazuril on LDH, NADH and NAD+ from the anaerobic stage of E. tenella (schizogony and gametogony); 4)EtLDH gene was transfected into yeast cells to verify the relationship between the EtLDH and diclazuril; 5) Flow cytometry was used to study the effect of NAD+ and ATP on the invasion capability of sporozoites and merozoites after treated with diclazuril.. Theses studies not only could help to understand the role of lactic dehydrogenase in the mechanism of diclazuril against E. tenalla, but also to learn more about the biological function of EtLDH. These would have important theoretical significance and practical value to clarify the anti-coccidial molecular mechanisms of diclazuril and discover new anticoccidial-drug targets.