Taurine, inhibitor
Taurine, NH2-CH2-CH2-SO3 H, is thus named because it was isolated initially in the bile of bullsl. Its structure approaches that of GABA.
Metabolism
Taurine is present in the diet and is well absorbed by the digestive tract. It is also synthesized in the body. Its biosynthesis, which is carried out from methionine through cysteine, involves several steps. B6 vitamin is involved as a coenzyme in three of them.
Taurine is present in different tissues, particularly brain, retina and myocardium.
Its intracellular concentration is 500 to 2000 times higher than its extracellular concentration; and it is involved in regulation of osmotic exchanges.
Taurine penetrates into cells by co-transport with sodium which is then pumped out of cells by Na+/K+ATPase. Its intra-myocardial concentration rises in congestive heart failure by increase in its intracellular penetration, and its plasma concentration rises in patients with myocardial infarction.
Effects
Literature data concerning the role of taurine as a transmitter are less precise than those which relate to GABA. But it is known that it induces penetration of chloride ions inside cells, which increases their polarization. Taurine has the following effects:
- GABA-like effects, in particular the antiepileptic effect which is reinforced in the presence of zinc.
- Cardiac anti-arrhythmic and inotropic actions. The decrease of intramyocardial taurine concentration could worsen cardiomyopathies.
- Protective effect against intracellular calcium overload. Taurine modulates calcium concentration by increasing its uptake by sarcoplasmic reticulum and by inducing its extrusion out of the cell by stimulation of calcium-ATPase.
Applications
There is at present no drug whose principal mechanism of action is a modulation of synthesis or release of taurine.
Taurine itself is not marketed. One of its derivatives, acamprosate or acetylhomotaurinate, is used in treatment of alcoholic addiction and more precisely in maintenance of abstinence of alcohol-dependant patients by reducing craving for alcohol.
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