Serum Lactic Dehydrogenase and Ribonuclease in the Diagnosis of Malignant Tumours in Children.

In recent years increasing attention hasbeen given to the fluctuations of serum enzymes in neoplastic disease. It is thought that increased activity of certain enzymes in cancer cells and in damaged tissues results in the release of enzymes into the serum. Among many enzymes that have recently received interest, in relation to malignant neoplasia, are lactic dehydrogenase (SLD) (Wr6blewski, 1957, 1959; Blanchaer, Green, Maclean, and Hollenberg, 1958) and ribonuclease (RN-ase) (Wr6blewski, 1961). In 1930 Warburg, while investigating the metabolism ofneoplastic tissue, showed that in carcinomatous cells respiration was irreversibly impaired, with the consequence that there was increased anaerobic glycolysis. In spite of Warburg's discovery it was not until 1954 that Hill and Levi showed that the activity of lactate dehydrogenase, the end-enzyme of anaerobic glycolysis, rose in the serum of some patients with neoplastic disease. At present SLD activity seems to be a factor of some importance in the biochemical diagnosis of malignant neoplasia in adults (Wroblewski, 1961). Unfortunately, SLD can also be influenced by disease states other than malignant neoplasia, nor is its activity always increased in cancer (Zimmerman and Weinstein, 1956). No data are available on SLD activity in children with malignant tumours, though the problem merits special attention since lactic dehydrogenase activity in tissues of the foetus and newborn is much higher than in adults. LD is a soluble enzyme located primarily in cytoplasm, so it would enter the blood more readily than would the insoluble enzymes located in mitochondria. Taking into consideration the high LD activity in young cells, one would expect SLD to be a much more sensitive index of neoplastic processes in newborns and very young children than in adults. Available data on serum RN-ase activity mainly