3. Physiological and therapeutic roles of taurine in the heart

Taurine is the most abundant free amino acid in the heart. However, unlike the classical β-amino acids, taurine is a β-amino acid with the acid moiety being a sulfonic acid group rather than a carboxyl group; the lack of a carboxyl group excludes the involvement of taurine in peptide bond formation. Nonetheless, there is abundant evidence that taurine is an essential nutrient in certain species [1, 2] and semi-essential in other species [3]. Because of its abundance in the heart, there has been renewed interest in its role in contractile function. The initial evidence that taurine is essential for normal cardiovascular function was uncovered using nutritional and taurine transport inhibitor models of taurine depletion. While the nutritional deficiency studies have established a link between taurine depletion and the development of a cardiomyopathy, the nutritional model is difficult to reproduce. By comparison, the taurine transport inhibitor model is easy to reproduce but the interpretation of the results is problematic because of the side effects of the transport inhibitors. Because the heart depends upon an extracardiac source of taurine to maintain its large