ACTIVITY OF ASPARTATE AMINOTRANSFERASE ISOENZYMES WITH RELATION TO BODY WEIGHT AND PYRIDOXAL 5′-PHOSPHATE ACTIVITY IN THE MALIGNANT HYPERTHERMIA-SUSCEPTIBLE PIG

Abstract

The objective of the present study was to demonstrate in pigs the influence of halothane susceptibility on the activities of aspartate aminotransferase (AST) and its isoenzymes (m-AST and c-AST) during the postweaning period. Furthermore, the effects of pyridoxal 5′-phosphate (PLP) addition to the reaction mixture was also investigated. Seven different body weight levels were considered (group 1, 10–20 kg; group 2, 21–30 kg; group 3, 31–40 kg; group 4, 41–50 kg; group 5, 51–60 kg; group 6, 61–70 kg; group 7, more than 70 kg). The halothane challenge test was used to determine the MH susceptibility. Significantly greater plasma total AST activity (P < 0.05) was found in the malignant hyperthermia-susceptible (SMH) pigs compared to the resistant (RMH) for body weight groups 4 and 7. The addition of PLP enhanced the activity of AST on an average of 28%, and a significant difference between SMH and RMH was found in body weight group 4. m-AST was not affected by growth and similar values were found in both RMH and SMH groups of pigs. The addition of PLP enhanced the m-AST activity by an average of 35%. The activity of c-AST and c-AST-PLP showed a similar pattern to that of total AST with or without the coenzyme. Plasma of SMH and RMH pigs contain some apoenzyme which can be reactivated by PLP. Overall, AST and c-AST are significantly higher in SMH pigs and their activities correlate with body weight. Key words: Malignant hyperthermia, pig, AST-isoenzyme