同: COHb, HbCO
関: Carboxyhemoglobin

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hemoglobin

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/05/02 16:17:08」(JST)

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A heme unit of human carboxyhemoglobin, showing the carbonyl ligand at the apical position, trans to the histidine residue.^[1]

Carboxyhemoglobin (British English: Carboxyhaemoglobin) (COHb) is a stable complex of carbon monoxide and hemoglobin that forms in red blood cells when carbon monoxide is inhaled or produced in normal metabolism. Large quantities of it hinder delivery of oxygen to the body. Tobacco smoking (through carbon monoxide inhalation) raises the blood levels of COHb by a factor of several times from its normal concentrations. It is bright, cherry red.

Carbon monoxide as poison

Hemoglobin binds to carbon monoxide preferentially compared to oxygen (approx 240:1),^[2] so effectively, COHb will not release the carbon monoxide, and therefore hemoglobin will not be available to transport oxygen from the lungs to the rest of the body.

In large quantities, the effect of COHb is death - known medically as carboxyhemoglobinemia^[3] or carbon monoxide poisoning.^[4] However in smaller quantities COHb leads to oxygen deprivation of the body causing tiredness, dizziness and unconsciousness.

COHb has a half-life in the blood of 4 to 6 hours, but in cases of poisoning, this can be reduced to 70 to 35 minutes with administration of pure oxygen (the lower number applying when oxygen is administered with 4 to 5% CO2 to cause hyperventilation).

COHb increases risk of blood clot. It is thought that through this mechanism smoking increases the risk of having an ischemic stroke.

Pregnant smokers may give birth to babies of a lower birth mass. One theory is that, since fetal hemoglobin takes up carbon monoxide more readily than in an adult, therefore the fetus of a smoker will suffer from mild hypoxia, potentially retarding its development.

Carbon monoxide as normal biological metabolite

In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on the heme from hemoglobin breakdown. This process produces a certain amount of carboxyhemoglobin in normal persons, even if they do not breathe any carbon monoxide.

Following the first report that carbon monoxide is a normal neurotransmitter in 1993,^[5] as well as one of three gasses which naturally modulate inflammatory responses in the body (the other two being nitric oxide and hydrogen sulfide), carbon monoxide has received a great deal of clinical attention as a biological regulator. In many tissues, all three gases are known to act as anti-inflammatories, vasodilators and encouragers of neovascular growth.^[6] However, the issues are complex, as neovascular growth is not always beneficial, since it plays a role in tumor growth, and also the damage from wet macular degeneration, a disease for which smoking (a major source of carbon monoxide in the blood, several times more than natural production) increases the risk from 4 to 6 times.

Carbon monoxide as beneficially active substance, and potential pharmaceutical

Studies involving carbon monoxide have been conducted in many laboratories throughout the world for its anti-inflammatory and cytoprotective properties. These properties could potentially be used to prevent the development of a series of pathological conditions including ischemia reperfusion injury, transplant rejection, atherosclerosis, severe sepsis, severe malaria or autoimmunity. Clinical tests involving humans have been performed, however the results have not yet been released.^[7]

References

^ Gregory B. Vásquez, Xinhua Ji, Clara Fronticelli, Gary L. Gilliland (1998). "Human Carboxyhemoglobin at 2.2 Å Resolution: Structure and Solvent Comparisons of R-State, R2-State and T-State Hemoglobins". Acta Crys. D 54 (3): 355–366. doi:10.1107/S0907444997012250.
^ West JB: Respiratory Physiology -the essentials, 5th Ed. Williams & Wilkins, 1995, p. 76
^ López-Herce J, Borrego R, Bustinza A, Carrillo A (September 2005). "Elevated carboxyhemoglobin associated with sodium nitroprusside treatment". Intensive Care Med 31 (9): 1235–8. doi:10.1007/s00134-005-2718-x. PMID 16041521.
^ Roth D, Hubmann N, Havel C, Herkner H, Schreiber W, Laggner A (July 2009). "Victim of Carbon Monoxide Poisoning Identified by Carbon Monoxide Oximetry". J Emerg Med. doi:10.1016/j.jemermed.2009.05.017. PMID 19615844. http://linkinghub.elsevier.com/retrieve/pii/S0736-4679(09)00407-7.
^ New York Times article. Accessed May 2, 2010
^ Li L, Hsu A, Moore PK. Actions and interactions of nitric oxide, carbon monoxide and hydrogen sulphide in the cardiovascular system and in inflammation--a tale of three gases! Pharmacol Ther. 2009 Sep;123(3):386-400. PMID 19486912
^ Johnson, Carolyn Y. (October 16, 2009). "Poison gas may carry a medical benefit". The Boston Globe. http://www.boston.com/news/local/massachusetts/articles/2009/10/16/poison_gas_may_carry_a_medical_benefit/?page=full. Retrieved October 16, 2009.

External links

MeSH Carboxyhemoglobin

References

English Journal

CO binding improves the structural, functional, physical and anti-oxidation properties of the PEGylated hemoglobin.

Wang Q1, Hu T, Sun L, Ji S, Zhao D, Liu J, Ma G, Su Z.
Artificial cells, nanomedicine, and biotechnology.Artif Cells Nanomed Biotechnol.2015 Feb;43(1):18-25. doi: 10.3109/21691401.2014.885444. Epub 2014 Mar 19.
Abstract Context: PEGylated hemoglobin (Hb) is a promising oxygen therapeutic agent for clinical application. However, it suffered from structural perturbation, functional instability and methemoglobin (metHb) formation.OBJECTIVE: To improve the structural, functional, physical and anti-oxidation pr
PMID 24641771

Comparison of total haemoglobin mass measured with the optimized carbon monoxide rebreathing method across different Radiometer™ ABL-80 and OSM-3 hemoximeters.

Turner G, Richardson AJ, Maxwell NS, Pringle JS.
Physiological measurement.Physiol Meas.2014 Dec;35(12):N41-9.
A new Radiometer™ hemoximeter (ABL-80) has recently become available to measure carboxyhaemoglobin concentration for the optimized CO-rebreathing method (oCOR-method). Within the English Institute of Sport (EIS), hemoximeters are used in three different laboratories; therefore, precision and agree
PMID 25420054

Edaravone attenuates brain damage in rats after acute CO poisoning through inhibiting apoptosis and oxidative stress.

Li Q1, Bi MJ, Bi WK, Kang H, Yan LJ, Guo YL.
Environmental toxicology.Environ Toxicol.2014 Oct 28. doi: 10.1002/tox.22052. [Epub ahead of print]
Acute carbon monoxide (CO) poisoning is the most common cause of death from poisoning all over the world and may result in neuropathologic and neurophysiologic changes. Acute brain damage and delayed encephalopathy are the most serious complication, yet their pathogenesis is poorly understood. The p
PMID 25348283

Japanese Journal

Influence of HbCO Structure of the Bar-Headed Goose on Photolysis Thermodynamics as Studied by the Nanosecond Laser-Ultrasonic Technique

ZHAO Jin-yu,LI Jia-huang,ZHANG Zheng [他]
Bioscience, Biotechnology, and Biochemistry 77(6), 1251-1257, 2013-06
NAID 40019679629

Influence of HbCO Structure of the Bar-Headed Goose on Photolysis Thermodynamics as Studied by the Nanosecond Laser-Ultrasonic Technique

ZHAO Jin-yu,LI Jia-huang,ZHANG Zheng,ZHANG Shu-yi,QU Min,HUA Zi-qian,SHUI Xiu-ji,HUA Zi-chun
Bioscience, Biotechnology, and Biochemistry 77(6), 1251-1257, 2013
… To explore the structural differences in Hbs as between high and low altitude species, photolysis dynamic parameters, including quantum yield, enthalpy, and conformational volume changes in carboxy-Hbs (HbCO) for the bar-headed goose and low altitude counterparts (the Chinese goose and chicken) were investigated by the laser pumping-probing technique and photoacoustic calorimetry. …
NAID 130003361102

Determination of myoglobin concentration in blood-perfused tissue

Masuda Kazumi,Truscott Kent,Lin Ping-Chang,Kreutzer Ulrike,Chung Youngran,Sriram Renuka,Jue Thomas
European Journal of Applied Physiology 104(1), 41-48, 2008-09
… However, using the distinct 1H NMR signals of MbCO and HbCO yields a Mb concentration of 0.26 mM in both buffer- and blood-perfused myocardium. …
NAID 120001130311

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