Metabolic responses to exercise in the racehorse: changes in plasma alanine concentration

Abstract

Previous studies in humans have shown that alanine is released from the skeletal muscle in proportion to the work load. We have measured plasma alanine and urea concentrations in well-trained Standardbred and Finnish-bred (cold-blooded) trotters after a graded-intensity exercise and during recovery to study metabolic responses to exercise in this animal model. As controls we measured blood lactate, pyruvate, and glucose concentrations as well as hematocrit values. Metabolic responses to exercise were closely reflected in all these parameters. Plasma alanine increased relatively more than plasma lactate at moderate-intensity exercise near anaerobic threshold. The linear correlation between the intensity of exercise and plasma alanine was similar to that observed earlier in humans. Interestingly, plasma alanine concentrations remained elevated long after the submaximal exercise, whereas the concentration of lactate, pyruvate, and glucose decreased more rapidly. No significant changes were found in plasma urea concentration under these conditions. The most significant differences in the metabolic responses to exercise of the two breeds studied were the higher lactate-to-pyruvate ratios achieved during the high-intensity exercise and the more sensitive increases of plasma alanine even during low-intensity exercise in the Finnish-bred horses. These differences probably reflect different compositions of muscle fiber types in the two breeds. The findings together indicate that plasma alanine is greatly increased in the racehorse during and after a high-intensity exercise and thus is an important vehicle in transporting ammonia and carbon skeletons of products of anaerobic glycolysis out of the muscle tissue.

Exercise performance indices in normal and anabolic steroid treated trotters

“…Maximal lactate concentration after the MET was slightly, but not signifigantly (b0.05), lower in AS Group after the anabolic steroid treatment ( Table 2). The measured values are comparable to previously reported values in Finnhorses after a similar type of test on a racetrack (Poso et al 1987).…”

Plasma atrial natriuretic peptide in Standard bred and Finnhorse trotters during and after exercise

“…Although variations have been reported between horse breeds, e.g. in relation to blood volume, heart and spleen weight, muscle fibre composition or metabolic response to exercise (Persson 1967, Poso et al 1987, Kline & Foreman 1991), interbreed differences between Standardbreds and Finnhorses in ANP release seemed to be minor in the present study. Besides our preliminary report (Kokkonen et al 1993), there are no reports on the ANP release in Finnhorses.…”

Changes of Plasma Amino Acid and Inorganic Ion Concentrations with Maximum Exercises in Thoroughbred Young Horses

“…Concentrations of alanine and K+ in plasma significantly increased after exercise both BA+ and BA-types same as previous papers [9][10][11]. This result might suggest that these substances are released from skeletal muscles to plasma [9,10]. However, the increasing rate of plasma alanine of BA+ type was higher than that of BA-type.…”

“…The cause of this result is not clear. It is one possibility that the changes of these three amino acid concentration in plasma during exercise may be controlled by activity of urea pro duction in liver [9].…”

“…Plasma alanine and K+ concentrations in racehorses increase during exercise [9][10][11]. The increase of plasma alanine is acceler ated by the high levels of pyruvate produced from glycolytic pathway in the skeletal muscle by exercise [11].…”