The toxicological effects of some avermectins on goat liver carbonic anhydrase enzyme

Avermectins are used worldwide as antiparasitic drugs in the field of veterinary medicine and as agricultural pesticides and insecticides. Carbonic anhydrase (CA, E.C. 4.2.1.1) is a zinc‐containing metalloenzyme that catalyzes the reversible hydration of carbon dioxide (CO₂) to yield protons (H⁺) and bicarbonate (HCO₃^?). In this study, some avermectins, including abamectin, doramectin, eprinomectin, and moxidectin, were investigated for in vitro inhibitory effects on the CA enzyme purified from goat liver, which was purified (125.00‐fold) using sepharose 4B‐l ‐tyrosine‐sulfanilamide affinity chromatography, with a yield of 68.27% and a specific activity of 21765.31 EU/mg proteins. The inhibition results obtained from this study showed K_i values of 0.283, 0.153, 0.232, and 0.317 nM for abamectin, doramectin, eprinomectin, and moxidectin, respectively. On the other hand, acetazolamide, well‐known clinically established CA inhibitor, possessed a K_i value of 0.707 nM against goat liver CA.     

Positive and negative electrospray LC-MS-MS methods for quantitation of the antiparasitic endectocide drugs, abamectin, doramectin, emamectin, eprinomectin, ivermectin, moxidectin and selamectin in milk

Avermectin endectocides are used for the treatment of cattle against a variety of nematode and arthropod parasites, and consequently may appear in milk after normal or off-label use. The compounds abamectin, doramectin, and ivermectin, contain only C, H and O and may be expected to be detected by LC-MS in negative ion mode. The others contain nitrogen in addition and would be expected to be preferentially ionized in positive mode. The use of positive ion and negative ion methods with electrospray LC-MS-MS were compared. Using negative ion the compounds abamectin, doramectin, ivermectin, emamectin, eprinomectin, and moxidectin gave a curvilinear response and were quantified in raw milk by LC-MS-MS with a triethylamine-acetonitrile buffer over the concentration range 1-60 ppb (microg/kg) using selamectin as the internal standard. The limits of detection (LOD) were between 0.19 ppb (doramectin) and 0.38 ppb (emamectin). The compounds gave maximum sensitivity with positive ionisation from a formic acid-ammonium formate-acetonitrile buffer and were detected in milk (LC-MS-MS) also with a curvilinear response over the range 0.5-60 ppb. Although the positive ion signals were larger, with somewhat lower limits of detection (LOD between 0.06 ppb (doramectin) and 0.32 ppb (moxidectin) the negative ion procedure gave a more linear response and more consistent results. Comparison of spiked samples in the range 2-50 ppb showed a high degree of correlation between the two methods.     

Effect of intravenous nitroglycerin therapy on erythrocyte antioxidant enzymes

Intravenous nitroglycerin (GTN) has been used as an anti-ischemic agent for the therapy of unstable and post-infarction angina. Nitric oxide (^?NO) and S-nitrosothiols constitute the biologically active species formed via nitroglycerin bioactivation. Increased levels of reactive oxygen species can diminish the therapeutic action of organic nitrates by scavenging donated ^?NO and oxidizing tissue thiols important in nitrate biotransformation. Studies reported here show that the red cell activity of antioxidant enzymes, catalase and glutathione peroxidase, are significantly decreased after intravenous nitroglycerin treatment. Catalase activity decreased to and after 1 and 24?hr GTN infusion, respectively. Similarly, glutathione peroxidase activity decreased to and after 1 and 24?hr GTN infusion, respectively. The reported decrease in antioxidant enzyme activities can lead to an oxidant milieu and contribute to the generation of nitrate tolerance.