SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
Other Enzymes
Effects of exercise and training on plasma concentrations of other enzymes have been less well studied . Gamma gutamyl transferase ( GGT ) concentrations are apparently unaffected by endurance training or racing . However , GGT concentrations may be higher in 2-year-old Thoroughbreds that have been in training for a limited time ( less than 3 months ), when values are compared to those of older and more trained racehorses . It seems that horses have much higher GGT levels in skeletal muscle than other species . Also , it cannot be discounted that these mild increases in GGT are indicative of infections with the recently reported non-primate hepacivirus and / or equine pegivirus .
Transient increases in alkaline phosphatase concentrations have been observed following prolonged submaximal exercise and after a maximal gallop over 1000 m in 60 seconds . The magnitude of these increases were small and concentrations had returned to resting levels within an hour after exercise .
CREATININE , UREA AND BILIRUBIN
Creatinine , urea and bilirubin concentrations all increase following prolonged exercise . Elevations in creatinine and bilirubin have also been seen following maximal exercise , although less consistently . Creatinine and urea concentrations probably are elevated as a result of a higher metabolic rate , with associated increases in the rate of phosphocreatine utilization in the muscle ( creatinine ) and the gluconeogenic catabolism of protein ( urea ). In endurance exercise , small reductions in glomerular filtration rate secondary to loss of plasma volume may also develop , as a decrease in urinary creatinine excretion was identified in one study . This finding , plus the increased duration of work in endurance events , may explain why increases in plasma creatinine and urea concentrations are more marked following that type of exercise . Although values rise , the actual increases are small , and it is uncommon to record creatinine concentrations greater than 2.7 mg / dl or urea concentrations above 30 mg / dl . Values in excess of these figures may signify a developing clinical problem , and further close examination of the horse would be warranted .
Bilirubin concentrations seem to be elevated for at least 3 days after racing ( both track and endurance ). It would appear that this is due to hemolysis which likely accompanies most forms of equine exercise , and is apparently due to increases in the fragility of the erythrocytes . Whether this is because erythrocytes entering the circulation are older or younger and more prone to lyse , or whether it reflects the effects on the red cell membrane of fluid and electrolyte shifts remains to be determined . In fact , it has been hypothesised that increased bilirubin concentrations are due to fasting rather than erythrocyte turnover , because haptoglobin concentrations do not change with training . Whatever its origin , the hyperbilirubinemia associated with exercise does not seem to be indicative of decreased hepatic function .
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