Tissue Dilution Artefact; a Re-interpretation of Variations in Levels of Succinic Dehydrogenase during Chemical Carcinogenesis

Abstract

RECENT biochemical studies on succinic dehydrogenase in livers of rats fed with the liver carcinogen p-dimethylaminoazobenzene (DAB) for periods of up to 150 days have confirmed the well-established phenomenon that the level of this enzyme generally falls as feeding progresses (Table 1). Samples of tissue from each liver lobe were taken for histological and histochemical investigations, and the remainder was homogenized. Succinic dehydrogenase was estimated to within an accuracy of ± 10 per cent by the anaerobic methylene blue technique, basing the Q_MB values on dry weight. For histochemical purposes the tissue was frozen¹, stored for not longer than a week, and cut at − 20° C. in a refrigerated microtome. Succinic dehydrogenase was detected higtochemically by incubating frozen sections in a neotetrazolium-succinate buffer system²; in addition, the periodic acid–Schiff method³ was used to stain glycogen, while phospholipid was stained by the acid hæmatin method⁴.