Hepatoprotective activity of angiotensin-converting enzyme (ACE) inhibitors, captopril and enalapril, against paraquat toxicity

Paraquat is a highly toxic herbicide that is used in most countries without restriction. The cytotoxic action of paraquat is mediated by reactive radicals that are products of its metabolic reduction in cells. It has already been hypothesized that some angiotensin-converting enzyme inhibitors (e.g., captopril and enalapril) could show antioxidant and radical scavenging activity through their structural thiol groups, increasing antioxidant enzymes production or nitric oxide synthesis. In this study the hepatoprotective effect of captopril and enalapril against paraquat induced oxidative stress cytotoxicity was evaluated in isolated rat hepatocyte. Subtoxic concentrations of captopril (0.2 mM) and enalapril (0.2 mM) significantly (p < 0.05) protected the hepatocytes against paraquat (2 mM) induced oxidative stress cytotoxicity markers including: cell lysis, reactive oxygen species (ROS) generation, lipid peroxidation, glutathione depletion, mitochondrial membrane potential decrease, lysosomal membrane oxidative damage and cellular proteolysis. Moreover, we showed that non-thiol enalapril acts as well as thiol containing captopril at inhibiting oxidative stress cytotoxicity markers. Finally, our results support the hypothesis that it is the increase in nitric oxide synthesis and not the presence of the thiol group that accounts for the antioxidant activity of ACE inhibitors.     

NEM对川百合花粉萌发和花粉管伸长的抑制效应

为探明微丝骨架结构以及微丝骨架对花粉萌发和花粉管伸长的作用,采用不同浓度的巯基类化学反应试剂NEM处理川百合花粉。结果表明:30μmol/L NEM能有效抑制川百合花粉萌发和花粉管伸长,抑制率分别达到95%和99%;经20μmol/L NEM处理过的川百合花粉,在去掉NEM后,其萌发率恢复到对照(0μmol/L NEM)的98%,花粉管长度恢复到对照(0μmol/L NEM)的60%;15μmol/L、20μmol/L和30μmol/L NEM处理过的川百合花粉,其花粉管内微丝排列呈弯曲状;而非沿纵轴向顶端延伸的正常微丝束状态。可见,NEM作为一种微丝骨架的抑制剂改变了花粉管中微丝骨架的分布结构,影响了花粉管的生长。     

Two typical K-efficiency cotton genotypes differ in potassium absorption kinetic parameters and patterns

As a macroelement to plant, potassium (K) absorption mechanism has been widely studied. However, as for cotton genotypes with different K efficiency, how they related to the absorption patterns under K starvation is not fully understood. In this hydroponic experiment, plants were grown at different K levels: low (K1, 2 mg/L) and adequate K level (K2, 20 mg/L) for 2 weeks. K⁺ absorption kinetic parameters were got by Michaelis–Menten equation. By applying K channel-blocking agent, tetraethylammonium and protein modifying reagent N-ethylmaleimide, we evaluated the differences in K absorption mechanisms for two typical cotton genotypes (K-efficient genotype 103 and K-inefficient genotype 122). Results showed that higher affinity to K⁺ and better root formation of genotype 103 resulting in better adaptation in low-K⁺ condition, whether grown in low or adequate K⁺ environment. Further study with K⁺ absorption inhibitors suggested the two genotypes grown in low-K⁺ environment absorbed K⁺ mainly by high-affinity K⁺ absorption systems, and for seedlings grown in adequate K condition, genotype 103 absorbed K⁺ with both K channels and high-affinity proton and mainly by high-affinity K channels, while genotype 122 absorbed K⁺ by K channels. These results indicated that the low-K condition could induce higher affinity to absorb K⁺, and the two cottons with different K efficiency mainly due to different low-K adaptation and absorb K⁺ with different patterns. This could provide a possible theory for the selection of K-efficient varieties.