Taurine antagonists

Kudo Y, Tanaka A, Yamada K. Dendrobine, an antagonist of beta-alanine, taurine and of presynaptic inhibition in the frog spinal cord. Br J Pharmacol 1983 78 709-715. 

Taurine (2-aminoethanesulfonic acid 4.235) is an inhibitory neurochemical that probably acts primarily as a neuromodulator rather than a neurotransmitter. It is formed from cysteine, and its accumulation can be prevented by the cardiac glycoside ouabain. Although receptor sites and specific actions cannot be elucidated without an antagonist, taurine has been implicated in epilepsy and, potentially, in heart disease. There are a large number of physiological effects attributed to taurine, among them cardiovascular (antiarrythmic), central (anticonvulsant, excitability modulation), muscle (membrane stabilizer), and reproductive (sperm motility factor) activity. Analogs of taurine, phthalimino-taurinamide (4.236) and its iV-alkyl derivatives, are less polar than taurine and are potent anticonvulsant molecules. 

Key Words niacin, taurine, pirfenidone, integrins, PAF-receptor antagonists, NOS inhibitors, cysteine pro-drugs... 

Taurine (2-aminoethanesulfonic acid) may have certain central inhibitory properties that qualify it for neurotransmitter status. At present only strychnine appears as a viable antagonist (as it is for gly), making it difficult to differentiate the central effects of these two amino acids. 

The crucial role played by vitamin Bg in the nervous system and in neuroendocrinology is based on the fact that various putative neurotransmitters as well as taurine, sphingolipids, and polyamines are synthesized by pyridoxal phosphate (PLP)-dependent enzymes. There are numerous biological effects of vitamin Bg unrelated to the role of PLP as a coenzyme. PLP is an antagonist of both the voltage-mediated and the ATP-mediated calcium transport systems. PLP modulates the activities of steroid hormone receptors and transcription factors. The preventive effect of vitamin Bg on tumorigenesis might also derive from the antioxidant functions of this vitamin. 

I will also describe a simple method of modifying taurine content, using a compound, guanidinoethyl sulfonate, which is a competitive antagonist of taurine transport, and which is also, in part, a physiological antagonist. 

It does not appear that events in the adrenergic cascade past the increase in cAMP concentrations are involved in the stimulation of taurine influx. For example, increased calcium influx does not appear to be a factor. If the increase in calcium flux produced by isoproterenol is blocked by the calcium antagonist verapamil, the increase in cAMP still occurs, as does increased taurine influx. 

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