Enzyme histochemistry of the adult liver fluke, Fasciola hepatica

Abstract

The distribution of seventeen enzyme systems has been investigated histochemically in the adult liver fluke, Fasciola hepatica. The enzymes studied were NAD diaphorase, NADP diaphorase, succinic dehydrogenase, glucose-6-phosphate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, glutamate dehydrogenase, α-glycerophosphate dehydrogenase, β-hydroxybutyrate dehydrogenase, acid phosphatase, alkaline phosphatase, glucose-6-phosphatase, esterase, adenosine triphosphatase, 5-nucleotidase, and cytochrome oxidase. Only two enzymes, β-hydroxybutyrate dehydrogenase and 5-nucleotidase, were entirely absent. Three enzymes of the tricarboxylic acid cycle in the fluke were shown to be present. Although the tegument has been thought to be responsible for absorption of food and excretion of waste materials, the gut is better equipped enzymatically for these functions. The small amount of glucose-6-phosphatase and the complete absence of β-hydroxybutyrate dehydrogenase is explained by the abundance of glycogen present in the fluke, which is probably supplied by the liver of the host animal. Despite the predominantly anaerobic nature of the respiration, cytochrome oxidase activity was detected in the fluke.