Cytochrome oxidase, inhibition

Usefulness of various biochemical indicators of cyanide poisoning, such as cytochrome oxidase inhibition (Gee 1987), estradiol and thyroxine levels in fish plasma (Ruby et al. 1986, 1993a), and pituitary gland histology (Ruby et al. 1993b)... 

NO also has cytotoxic effects when synthesized in large quantities, eg, by activated macrophages. For example, NO inhibits metalloproteins involved in cellular respiration, such as the citric acid cycle enzyme aconitase and the electron transport chain protein cytochrome oxidase. Inhibition of the heme-containing cytochrome P450 enzymes by NO is a major pathogenic mechanism in inflammatory liver disease. 

Research should be conducted in experimental animals to determine the lowest concentration that causes serious effects, such as severe eye irritation or damage. Data are limited on the exposure that result in eye irritation, particularly for the concentrations, conditions, and durations associated with the transition from irritation to irreversible eye damage. More data quantifying the effects of other chemicals in lowering the threshold for ocular toxicity also are needed. Research should also be conducted to elucidate the dose-response curve for cytochrome oxidase inhibition with increasing hydrogen sulfide concentrations (i.e., 15 ppm and above). 

The toxin, amygdalin, releases hydrocyanic acid. Thus, toxicity is similar to cyanide, and is dose-related. Cytochrome oxidase inhibition interrupts electron transport and oxygenation at the cellular level. 

Sodium azide is reactive compound that is widely used commercially as a propellant in automotive airbags. The azide anion is highly toxic and can present health hazards at high levels, in the form of headaches, cytochrome oxidase inhibition and vasodilation. Usage of azide in airbags increases contamination in... 

Amine A, Alafandy M, Kauffmann J, Pekli MN (1995) Cyanide determination using an amperometric biosensor based on cytochrome oxidase inhibition. Anal Chcan 67 2822-2827... 

Barbiturates such as amobarbital inhibit NAD-hnked dehydrogenases by blocking the transfer from FeS to Q. At sufficient dosage, they are fatal in vivo. Antin cin A and dimercaprol inhibit the respiratory chain between cytochrome b and cytochrome c. The classic poisons H2S, carbon monoxide, and cyanide inhibit cytochrome oxidase and can therefore totally arrest respiration. Malonate is a competitive inhibitor of succinate dehydrogenase. 

CBD has no activity at the CBl or CB2 receptor. It is well known that CBD influences the activity of THC if co-administered [140]. Another effect of CBD is the inhibition of cytochrome oxidase [141], which inversely to its antagonistic activity strongly potentiates THC effects above a certain threshhold. CBD is also active as a mild antipsychotic [142] and was proposed as a treatment for anxiety and panic attacks. The mechanism is not fully understood, but it might be caused by an interference with the endocannabi-... 

Female NMRI mice were exposed to 100 ppm of hydrogen sulfide for 2 hours at 4-day intervals excitement was observed (Savolainen et al. 1980). Exposure also resulted in decreased cerebral ribonucleic acid (RNA), decreased orotic acid incorporation into the RNA fraction, and inhibition of cytochrome oxidase. An increase in the glial enzyme marker, 2, 3 -cyclic nucleotide-3 -phosphohydrolase, was seen. Neurochemical effects have been reported in other studies. Decreased leucine uptake and acid proteinase activity in the brain were observed in mice exposed to 100 ppm hydrogen sulfide for 2 hours (Elovaara et al. 1978). Inhibition of brain cytochrome oxidase and a decrease in orotic acid uptake were observed in mice exposed to 100 ppm hydrogen sulfide for up to 4 days (Savolainen et al. 1980). 

The mechanism of hydrogen sulfide toxicity is in part similar to that of cyanide. Like cyanide, hydrogen sulfide can inhibit the enzyme cytochrome oxidase resulting in tissue hypoxia. Specific health effects are discussed in greater detail below. 

Hydrogen sulfide inhibits mitochondrial cytochrome oxidase, resulting in disruption of the electron transport chain and impairing oxidative metabolism. Nervous and cardiac tissues, which have the highest oxygen demand (e.g., brain and heart), are especially sensitive to disruption of oxidative metabolism (Ammann 1986 Hall 1996). 

L The answer is d. (Hardman, p 906.) Cimetidine slows the metabolism of Ca channel blockers, which are substrates for hepatic mixed-function oxidases. Inhibition of cytochrome P450 activity is peculiar to cimetidine and is not a mechanism of action of other histamine 2 (Hz) blockers. 

In higher plants, elevated cyanide concentrations inhibited respiration (through iron complex-ation in cytochrome oxidase) and ATP production and other processes dependent on ATP, such as... 

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