title: Application of a hepatocyte-erythrocyte coincubation system to studies of cyanide antidotal mechanisms.
abstract: A coincubation system composed of hepatocytes in primary monolayer culture and erythrocytes suspended in the culture medium was developed and used as a model for investigations of mechanisms of cyanide antidote action at the cellular level. Hepatocyte ATP was used as the cytotoxicity indicator. Treatment of rat hepatocytes in the coincubation system with KCN (1.0 mM) for 10 min at 37 degrees C selectively reduced hepatocyte ATP levels to 33 +/- 15% of control (no KCN added) levels. 4-dimethylaminophenol (DMAP), cobalt(II) chloride, sodium nitrite, sodium thiosulfate, or a combination of the last two antidotes added to the KCN-containing medium significantly reversed ATP depression and the response was concentration dependent. The relative effectiveness, on a molar basis, was estimated to be DMAP greater than CoCl2 much greater than NaNO2 congruent to Na2S2O3. NaNO2 and DMAP induced methemoglobin formation in the absence of cyanide and cyanmethemoglobin formation in its presence; erythrocytes were required in the medium for effectiveness. CoCl2 produced neither cyanmethemoglobin nor thiocyanate in appreciable quantities nor required erythrocytes for antagonism. Na2S2O3 converted cyanide to thiocyanate and reversed ATP depression without erythrocytes in the medium. The addition of erythrocytes increased these rates significantly and to a greater extent than albumin. The overall results are consistent with previously proposed modes of action for these antidotes. However, the enhancement in cyanide metabolism and ATP recovery with Na2S2O3 and erythrocytes in the system was unexpected and raises the possibility that erythrocytes may contribute to cyanide disposition and antagonism in vivo when this antidote is administered.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000627:Aminophenols / Q000494:pharmacology; D000818:Animals; D000931:Antidotes / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D003035:Cobalt / Q000494:pharmacology; D003486:Cyanides / Q000633:toxicity*; D004912:Erythrocytes / Q000166:cytology* / Q000378:metabolism; D066298:In Vitro Techniques; D008099:Liver / Q000166:cytology* / Q000378:metabolism; D008297:Male; D011190:Potassium Cyanide / Q000633:toxicity; D051381:Rats; D011919:Rats, Inbred Strains; D012977:Sodium Nitrite / Q000494:pharmacology; D013885:Thiosulfates / Q000494:pharmacology
chemical_list: D000627:Aminophenols; D000931:Antidotes; D003486:Cyanides; D013885:Thiosulfates; D003035:Cobalt; D000255:Adenosine Triphosphate; C018021:cobaltous chloride; C017717:sodium thiosulfate; D012977:Sodium Nitrite; D011190:Potassium Cyanide; C020292:4-dimethylaminophenol