Comparative effects of cytochrome P-450 inhibitors on Ca2+ and Mn2+ entry induced by agonists or by emptying the Ca2+ stores of human neutrophils.
The effects of cytochrome P-450 inhibitors of different chemical structures, including several imidazole antimycotics, SKF525A, 5,8,11,14-eicosatetraynoic acid (ETYA), gossypol and nordihydroguaiaretic acid (NDGA), were tested on the entry of Ca2+ and Mn2+ induced either by emptying the intracellular Ca2+ stores with thapsigargin or by stimulation with platelet activating factor (PAF). Most of the drugs inhibited thapsigargin-induced Ca2+ and Mn2+ entry with the same affinity, with the striking exceptions of econazole and miconazole, which were 5- and 2-fold more potent to inhibit the thapsigargin-induced Mn2+ entry than to inhibit Ca2+ entry, respectively. Additionally, high doses of every drug (3-10-times the Ki) activated a pathway permeable to Mn2+ and Ni2+ but not to Ca2+. These findings indicate that Mn2+ entry data should be interpreted with caution and always be cross-checked with Ca2+ uptake measurements. Most of the drugs inhibited PAF-induced Mn2+ uptake with an affinity similar to that found for thapsigargin-induced Mn2+ uptake. PAF- and thapsigargin-induced Ca2+ uptake were also inhibited similarly by NDGA, SKF525A and gossypol, but PAF-induced Ca(2+)-uptake was inhibited about 5-fold more strongly by econazole and ETYA and two-fold more strongly by miconazole and clotrimazole. These findings suggest that the Ca2+/Mn2+ entry pathway opened by agonists in human neutrophils is the same that activates on emptying the Ca2+ stores and that cytochrome P-450 activity may be involved en the activation of the channels.
Montero
M
M
Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid, Spain.
Garcia-Sancho
J
J
Alvarez
J
J
D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D065607:Cytochrome P-450 Enzyme Inhibitors; D004464:Econazole / Q000494:pharmacology; D016257:Fura-2; D006801:Humans; D007473:Ion Channels / Q000187:drug effects; D015759:Ionomycin; D008345:Manganese / Q000378:metabolism*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D009532:Nickel / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013729:Terpenes; D019284:Thapsigargin
D065607:Cytochrome P-450 Enzyme Inhibitors; D007473:Ion Channels; D010972:Platelet Activating Factor; D013729:Terpenes; D008345:Manganese; D015759:Ionomycin; D019284:Thapsigargin; C022838:nickel chloride; D004464:Econazole; D009532:Nickel; D002118:Calcium; D016257:Fura-2