Cyanide-induced alteration of cytosolic pH: involvement of cellular hydrogen ion handling processes.
Neuronal cells exposed to cyanide rapidly lose the capacity to regulate internal Ca2+ homeostasis, thereby accumulating an excess cytosolic Ca2+ load. The present study was undertaken to examine the effects of KCN on another important ion: hydrogen ion. KCN (1-10 mM) rapidly decreased intracellular pH (pHi) of cultured pheochromocytoma (PC12) cells as indicated by the pH-sensitive fluorescent dye 2',7-bis(carboxyethyl)-5(6)-carboxyfluorescein. Removal of Ca2+ from the media or pretreating the cells with diltiazem (10(-5) M), a calcium channel blocker, delayed the onset and reduced the magnitude of the drop in pHi. Lowering the pH of the incubation medium (pHo) to 6.9 exaggerated the drop in pHi, while raising it to 7.9 attenuated the change in pHi. Removal of Na+ from the media enhanced the cyanide effect. Reintroduction of Na+ or substitution with Li+ reversed the cytosolic acidification, suggesting involvement of the Na+/H+ exchanger in the cyanide action. Pretreatment of cells with amiloride, 0.2 mM, blunted the cytosolic acidification induced by KCN, possibly by decreasing intracellular Na+ accumulation and disrupting H+ efflux. Cyanide thus produces a rapid dysfunction of hydrogen ion handling mechanisms and this may play a role in cyanide neurotoxicity.
Maduh
E U
EU
Department of Pharmacology and Toxicology, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, Indiana 47907.
Borowitz
J L
JL
Isom
G E
GE
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000310:Adrenal Gland Neoplasms / Q000473:pathology / Q000648:ultrastructure; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D002999:Clone Cells / Q000378:metabolism; D003470:Culture Media; D003600:Cytosol / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010673:Pheochromocytoma / Q000473:pathology / Q000648:ultrastructure; D011190:Potassium Cyanide / Q000494:pharmacology*; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D003470:Culture Media; D005452:Fluoresceins; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D012964:Sodium; D011190:Potassium Cyanide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium