Taurine decrease, functional

In experiment 1, oral administration of P-Ala increased both dipeptide levels in the brain. The treatment also increased camosine, but decreased anserine levels in the breast muscle. In experiment 2, dietary p-Ala dose-dependently increased both dipeptide levels in the brain. However, both dipeptides in the breast muscle were not influenced. In experiment 3, oral administration of P-Ala increased both dipeptide levels in the brain. The treatment also increased both dipeptides in the breast muscle (Figure 1). In amino acids, taurine levels in the brain and breast muscle were significantly decreased in all experiments. It was previously reported that depletion of taurine altered functions of the muscle (De Luca et al, 1996) in rats. Dietary P-Ala might alter physiological functions of birds due to the depletion of tissue taurine. These results suggest that dietary p-ala could modify dipeptide levels in the brain and breast muscle of chickens and the effects would be altered by age and/or type of chickens. 

A quantitatively important pathway of cysteine catabolism in animals is oxidation to cysteine sulfinate (Fig. 24-25, reaction z),450 a two-step hydroxyl-ation requiring 02, NADPH or NADH, and Fe2+. Cysteine sulfinic acid can be further oxidized to cyste-ic acid (cysteine sulfonate),454 which can be decarbox-ylated to taurine. The latter is a component of bile salts (Fig. 22-16) and is one of the most abundant free amino acids in human tissues 455-457 Its concentration is high in excitable tissues, and it may be a neurotransmitter (Chapter 30). Taurine may have a special function in retinal photoreceptor cells. It is an essential dietary amino acid for cats, who may die of heart failure in its absence,458 and under some conditions for humans.459 In many marine invertebrates, teleosts, and amphibians taurine serves as a regulator of osmotic pressure, its concentration decreasing in fresh water and increasing in salt water. A similar role has been suggested for taurine in mammalian hearts. A chronically low concentration of Na+ leads to increased taurine.460 Taurine can be reduced to isethionic acid... 

Activation of the polyol pathway results in a decrease of NADPH and NAD+ these are necessary cofactors in redox reactions throughout the body. The decreased concentration of these cofactors leads to decreased synthesis of reduced glutathione, nitric oxide, myoinositol and taurine. Myoinositol is particularly required for the normal function of nerves. Sorbitol may also glycate the amino nitrogen on proteins such as collagen, forming AGEs. 

The functional significance of decreases in plasma taurine is uncertain. As the only known bioch nical f mction of taurine is conjugation with bile acids (Encrantz and Sjovall, 1959)> measurement of taurine pools in liver and bile could be helpful in assessing the potential functional effects of a taurine-deficient diet. Measurement of the cerebral pool of taurine might also be helpful in assessing the availability of taurine for its putative function as a neurotrans-... 

---