Taurine pools

In a beagle pup model of total parenteral nutrition, the liver pool of taurine decreases more rapidly than the plasma pool, whereas the bile taurocholate pool is much slower to reflect taurine deficiency (Malloy et al., in preparation). In short-term experiments in adult man (up to 9 days), the concentration of taurocholate reflected the concentration of taurine available in the liver and the diet rather than that in plasma and muscle, indicating that all taurine pools in man are not in equilibrium (Hardison 1978). 

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-... 

Taurine-deficient diets fed to human infants for 3- weeks (Gaull et al., 1977) and to kittens for 10 weeks (Sturman et al., 1978) have been reported to cause a decrease in plasma taurine concentrations. Because of the limited tissues available for assaying taurine in human infants, it is difficult to determine how accurately plasma taurine concentrations reflect the effect of a taurine-deficient diet on tissue taurine concentrations. In the taurine-deficient kitten, plasma was second to liver only as the most adversely affected taurine pool (sturman et al., 1978). The affect of a relatively short period of a... 

In summary, total parenteral nutrition in the beagle puppy provides a useful tool in which further to examine the consequences of taurine-deficient diets during development. These data suggest that the hepatic taurine pool is the pool most rapidly depleted during taurine deficiency. Hepatic CSAD activity in the beagle is increased in response to a taurine-deficient diet, but this response is not... 

It is apparent that the heart has the capability to biosynthesize taurine, and also to take it up from the circulation. We have initiated quantitative studies as to the relative contributions of these two sources. Rats were maintained on a diet containing taurine of a known specific activity. Rats were sacrificed at intervals, and the specific activity of taurine determined in various tissues. From this, the content of taurine that had been derived from dietary sources could be calculated, as shown in Table 1. By the 15th day, in all tissues except the liver, influx had accounted for 1/3 of the total taurine. The remainder must either arise from biosynthesis, or be part of the taurine pool present in the tissue at the beginning of the experiment. These data, at face value, appear to be inconsistent with the results of experiments described below using guanidinoethyl sulfonate, a transport inhibitor of taurine. 

In these experiments, decreases in taurine content of up to 80% were seen within two to three weeks. One interpretation of this apparent discrepancy is that recently influxed taurine is not equilibrating with the total taurine pool in the cell, but comprises a pool from which a high percentage of the effluxed taurine is derived in other words, a fraction of the total cell taurine turns over faster than the average. This is in keeping with previous findings of multiple pools of taurine in rat organs, as deduced from kinetic data (Sturman 1973). 

Sturman, Taurine pool sizes in the rat effects of vitamin B-6 deficiency and high taurine diet, J. Nutr., 103 1566 (1973). 

The experimental results reported demonstrate that in beef kidney cortices is present a small protein operating a one-side decarboxylation of lanthionine with the production of aminoethylcysteine which is furtherly degraded into cysteamine,hypotaurine and taurine as previously reported(21).At the present time cannot be claimed that this decarboxylase is specific toward lanthionine its activity on lanthionine could be an ancillary activity of another decarboxylase.However this activity on lanthionine demonstrate the presence in animal tissues of a new route which,via cysteamine,contributes to taurine pool.These results further confirm that cysteamine pathway appears to be the most important route... 

In addition to changing the physical properties of bile acids, conjugation also alters their physiological properties. On the basis of extremely limited evidence, it seems likely that the bile acid pool of animals with exclusively taurine conjugates is maintained chiefly by active absorption from the ileum. 

Figure 6. NMR spectrum of a neutralized perchloric acid extract prepared from three pooled rat hearts each perfused for 34 min with 5 mM glucose and 2 mM 90% enriched [3- C] propionate. The spectrum was obtained under the same conditions as that of Figure 1. Abbreviations in addition to those defined in Figure 1 are Gn4, Gnj and Gn2, glutamine C-4, C-3, and C-2, respectively T, andT2, taurine C-1 and taurine C-2, respectively, M3, M2, malate C-3 and malate C-2, respectively 87,3. succinate C-2 plus C-3.

Amino acids are the building blocks of proteins upon hydrolysis of plant and animal tissues, the 20 protein amino acids mentioned in Section I will usually be obtained. Amino acids are also found free (referred to as free-pool amino acids) in animal and plant tissues and in the blood of vertebrates and invertebrates. Qualitative and quantitative differences may exist in the free-pool amino acids of different species, and the significance of such variations is obscure. However, amino acid variations in species may be important in studies on the chemotaxon-omy of organisms (Gilbertson and Schmid, 1975). By way of an example of differences in free-pool amino acids in related organisms, the most abundant free-pool amino acids in the rat tapeworm, Hymenolepis diminuta, are alanine and glutamic acid. By contrast, the most abundant free-pool amino acids in tapeworms of elasmobranchs (sharks and rays) are glycine and taurine (von Brand, 1973). It should be remembered, however, that a variety of analytical techniques are used to determine free-pool amino acids, and some of the interspecific variations reported in the literature may actually reflect differences in analytical procedures used. 

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