Effect of regular training on the myocardial and plasma concentrations of taurine and?-amino acids in thoroughbred horses

Abstract

Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 +/- 1.2 mumol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 +/- 0.9 and 7.7 +/- 0.69 mumol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1 mumol/g wet weight (4.6 +/- 0.25 and 1.7 +/- 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 +/- 1.1 mumol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p < 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.

Changes in intramuscular amino acid levels in submaximally exercised horses - a pilot study

“…Most of the resting plasma levels of AA in the control trials of this study are in agreement with published data on standardbred totters or thoroughbreds of similar ages and exercised under comparable conditions (Pö sö et al, 1987(Pö sö et al, , 1991(Pö sö et al, , 1993King and Suleiman, 1998;Essen-Gustavsson and Jensen-Waern, 2002;Trottier et al, 2002;Hackl et al, 2008). Compared with the 2-h postprandial resting plasma levels reported by Coenen et al (2006), most AA in our study were slightly and some times clearly lower.…”

The effects of short intensive exercise on plasma free amino acids in standardbred trotters

“…Taurine can be assumed to be released from muscle, for it is one of the most abundant, free AAs in muscle tissue. It has a high muscle to plasma ratio in horses (King and Suleiman, 1998) and increasing plasma concentrations could indicate muscle damage and or leakage through muscle cell membranes (King and Suleiman, 1998; Cuisinier et al., 2001). Taurine has an important physiological function as osmoregulator (Warskulat et al., 2004) and plays an important role in cellular defences against free radical‐mediated damages (Dawson et al., 2002).…”

“…Previous studies have investigated changes in post‐absorptive AA levels (Johnson and Hart, 1974; Russell et al., 1986; Cabrera et al., 1996), AA concentrations during hepatic diseases (Gullick et al.,1980; Lessard et al., 1986) in association with grass sickness (McGorum and Kirk, 2001), or following exercise (Pösö et al., 1993). Regular training led to significantly increased concentrations of threonine in plasma and heart muscle of thoroughbred horses (King and Suleiman, 1998). Valine, isoleucine, leucine and phenylalanine levels tended to increase (King and Suleiman, 1998).…”

“…Regular training led to significantly increased concentrations of threonine in plasma and heart muscle of thoroughbred horses (King and Suleiman, 1998). Valine, isoleucine, leucine and phenylalanine levels tended to increase (King and Suleiman, 1998). Supplementation of branched‐chain amino acids (BCAA) had no significant effect on the performance of standardbred trotters leading the authors to the conclusion that exercising horses fed a balanced diet require no specific AA supplementation (Casini et al., 2000).…”