Quinidine-induced inhibition of leukocyte esterases.
We have demonstrated the feasibility of a system based on image processing to measure enzyme activity inside morphologically classified individual cells. When used in this system, quinidine inhibited naphthol AS-D chloroacetate esterase in polymorphonuclear neutrophils and alpha-naphthyl acetate esterase and alpha-naphthyl butyrate esterase in monocytes. These effects were dependent on the duration of exposure and on drug concentration. Dose-effect relationships were established and the concentration at which 50% inhibition (ID-50) occurred was used as a reference point to compare the toxicity of different compounds. Chloroquine, primaquine, and quinine (which, like quinidine, possess a quinoline ring) also affected the esterases, but had no effect on several other enzymes. Neostigmine inhibited the esterases we studied but only at a very high concentration. Various chemicals inhibited the enzymes within the cells, as has been demonstrated for the enzymes in plasma.
Markovic
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OT
Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia 19104-4283.
Young
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DS
Markovic
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NS
D000826:Animal Testing Alternatives; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors* / Q000097:blood; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007962:Leukocytes / Q000201:enzymology*; D008214:Lymphocytes / Q000201:enzymology; D009000:Monocytes / Q000201:enzymology; D009283:Naphthol AS D Esterase / Q000037:antagonists & inhibitors* / Q000097:blood; D009504:Neutrophils / Q000201:enzymology; D011802:Quinidine / Q000009:adverse effects / Q000494:pharmacology*
D009283:Naphthol AS D Esterase; D002265:Carboxylic Ester Hydrolases; C021855:naphthylbutyrate esterase; D011802:Quinidine