The Effect of Storage at — 80 °C on the Activities of Cytoplasmic, Mitochondrial and Microsomal Enzymes in Rat Liver

Publisher Website
Google Scholar
Abstract
The effect of storage -80.degree. C for 1-28 days on the activity of 12 enzymes [glucokinase, glucose-6-phosphate dehydrogenase, fructose-bisphosphatase, 6-phosphofructokinase, glutamate dehydrogenase, L-aspartate: 2-oxoglutrate aminotransferase, L-alanine: 2-oxo-glutarate aminotransferase, xanthine oxidase, ornithine carbamoyl transferase, glucose-6-phosphatase, citrate synthase and arginase] in intact liver tissue, liver extract and isolated hepatic microsomes was investigated. To find optimal conditions for tissue homogenization for this study, the effects of 3 types of homogenization on the activity of 10 enzymes [glutamate dehydrogenase, citrate synthase, L-aspartate: 2-oxoglutarate aminotransferase, L-alanine: 2-oxoglutarate aminotransferase, glucose-6-phosphate dehydrogenase, fructose-6-phosphate-kinase, hexokinase, glucokinase, D-fructose-bis-phosphatase, ornithine carbamoyl transferase] from different cell compartments were compared. The activities of glucokinase and phosphofructokinase decreased markedly during storage of both supernatant and liver tissue. Storage of liver tissue increased the activity of mitochondrial enzymes or isoenzymes. While this effect can be explained by additional disintegration of liver tissue caused by freezing and thawing for enzymes like glutamate dehydrogenase, other mechanisms may be involved in the prolonged increase observed in the activity of citrate synthase and xanthine oxidase storage. The activity of a number of enzymes from the cytosol, mitochondria and microsomes decreased more markedly in the stored liver samples than in the stored supernatant or in the stored microsomal pellet.