Mechanism of antagonizing cyanide-induced lethality by alpha-ketoglutaric acid.
alpha-Ketoglutaric acid (alpha-KG) has been shown to be an effective antagonist for cyanide-induced lethality. The mechanism of this antagonism is hypothesized to result from alpha-KG binding with cyanide. Several investigative approaches were taken to determine the existence of this binding. First, mixtures of various molar ratios of alpha-KG:cyanide were injected into a high pressure liquid chromatograph. The addition of cyanide reduced the peak area of alpha-KG at a molar ratio of greater than 1:5. Second, blood from naive male ICR mice was spiked with alpha-KG and cyanide. Headspace above these blood samples was injected into a gas chromatograph and analyzed for released hydrogen cyanide. alpha-KG reduced the peak area of hydrogen cyanide released into the headspace at molar ratios of greater than 1:2.5. Third, the effect of cyanide on the ultraviolet spectrum of alpha-KG was determined as an indication of binding. In the presence of cyanide the absorption peak at 316 nm for alpha-KG was eliminated. Inhibition of cytochrome oxidase is an accepted target enzyme for cyanide-induced lethality. Fourth, further evidence of alpha-KG's mechanism was determined by the effect of alpha-KG on brain cytochrome oxidase (BRCYTOX) and its ability to antagonize cyanide-induced inhibition of BRCYTOX. BRCYTOX activity was determined in the presence of alpha-KG and was found to be unaffected between 0.01 and 0.06 M of alpha-KG. Greater concentrations of alpha-KG inhibited BRCYTOX activity. The complete inhibition of BRCYTOX activity by 10(-5) M cyanide was prevented with 0.05 and 0.06 M alpha-KG. Fifth, BRCYTOX activity of animals pretreated with saline and then an LD80 dose (8.5 mg/kg) of cyanide was 80% inhibited, while BRCYTOX activity of animals pretreated with 2 g alpha-KG/kg, i.p., and then an LD80 dose (7.75 mg/kg) of cyanide was not different from control values. Thus, these data suggest that alpha-KG does bind with cyanide, and this binding can account for the antagonism of cyanide-induced lethality.
Norris
J C
JC
Bushy Run Research Center, Mellon Institute/Union Carbide Corporation, Export, PA 15632.
Utley
W A
WA
Hume
A S
AS
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology; D002851:Chromatography, High Pressure Liquid; D003486:Cyanides / Q000037:antagonists & inhibitors*; D003576:Electron Transport Complex IV / Q000378:metabolism; D007274:Injections, Intraperitoneal; D007656:Ketoglutaric Acids / Q000378:metabolism / Q000627:therapeutic use*; D007928:Lethal Dose 50; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D011190:Potassium Cyanide / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000633:toxicity
D003486:Cyanides; D007656:Ketoglutaric Acids; D003576:Electron Transport Complex IV; D011190:Potassium Cyanide