Activities of enzymes in the malate-aspartate shuttle in the peripheral leukocytes of dogs and cats

The activities of the enzymes involved in the malate-aspartate shuttle and the expression of malate dehydrogenase (MDH), a rate-limiting enzyme in the NADH shuttle that produces ATP in glucose metabolism in leukocytes, were d etermined to investigate the differences in this shuttle system in the peri pheral leukocytes of dogs and cats. There were no significant differences b etween dogs and cats in plasma glucose, immunoreactive insulin, free fatty acid or triglyceride concentrations. The activities of cytosolic and mitoch ondrial MDH and of mitochondrial glutamate dehydrogenase (GLDH) in canine l eukocytes were significantly higher than in feline leukocytes. High activit ies of MDH in canine leukocytes were confirmed by RT-PCR analysis on the to tal RNA extracted from leukocytes. It was concluded that there were signifi cant differences between dogs and cats in the NADH shuttle system.