Histochemical Demonstration of 5-Nucleotidase Activity in Cell Nuclei

Intracellular distribution of 5' nucleotidase in rat liver

The intracellular distribution of 5' nucleotidase was investigated in rat liver by biochemical analysis of cell fractions obtained by differential centrifugation. The enzymatic activity was measured by determination of the inorganic phosphorus liberated from 5' nucleotides. The 5' nucleotidase activity was mainly found in the nuclear and microsomal fractions. An attempt to extract the enzyme from these fractions with Mg⁺⁺ ion solutions was unsuccessful. It is concluded that 5' nucleotidase is actually present in the nuclear and microsomal fractions of rat liver cells.

Distribution of glucose-6-phosphatase and 5-nucleotidase in the digestive system of two teleost fishes

The distribution and histochemical localization of G6Pase and 5-nucleotidase in the different parts of the alimentary canal of two teleost fishes, Heteropneustes fossilis and Barbus sophore have been studied. The major sites of activity of the two enzymes are intestinal mucosa and liver. G6Pase is localized in the cytoplasm of the absorptive cells of the intestinal mucosa while 5-nucleotidase is present in the cytoplasm as well as nucleus and cell membrane. In the intestine, the anterior portion shows more stronger activity than in the middle and posterior portions. Mild activity is also noticed in the mucosa and gastric glands of the stomach. G6Pase activity is stronger than 5-nucleotidase activity in all the portions. Weak 5-nucleotidase activity is found in the submucosal connective tissue and the nuclei of the intestine. The goblet cells, muscularis abd serosa are negative in all the portions. G6Pase activity is stronger in the herbivorous fish Barbus sophore than in the omnivorous form Heteropneustes fossilis. In the liver, stronger activity of two enzymes is localized in the hepatocytes surrounding the sinusoids. Connective tissue and endothelial lining are negative.

Localization of 5'-ribonucleotide phosphohydrolase in regenerating (and normal) limb tissues of the adult newt Notophthalmus viridescens

The regenerating forelimb of the adult newt, Notophthalmus viridescens was investigated for 5'-nucleotidase (5' ribonucleotide phosphohydrolase, 3.1.3.5) acitivity. The newt's humeri were surgically removed, and after a twenty-one-day recovery period, the forelimbs amputated above the elbows. Regenerates were sampled at predetermined times for specific phases in the progress of regeneration, frozen, sectioned in a cryostat, and the sections fixed in 10% cold formol calcium. The Wachstein and Meisel [25] lead procedure at neutral pH was used predominately in these experiments, although tests were also conducted with Gomori's [14] calcium, Allen's [21] highly alkaline procedures. The substrates used to obtain specific enzyme reactions were adenine, cytosine, guanine, uracil and inosine 5'-monophosphate nucleotides. Sodium beta-glycerophosphate served as a non-specific phosphomonoesterase substrate, distilled water replaced substrate, and inhibitors such as zinc and cyanide ions were used as control measures to assist in increasing the precision in interpreting the results obtained. The most reactive 5'-nucleotidase (5'-Nase) loci were in the walls of the blood vascular system, mysial and neural sheaths, dermis, and periosteum: the principal cells involved were macrophages, endothelium of blood vessels, and fibrocytes of connective tissues. A moderate enzyme response was elicited from secretory cells of some of the subcutaneous glands, hypertrophied chondrocytes and osteogenic centers, chondrocytes in the articular regions and within red blood cells and leucocytes. Normal, injured and degenerating, or regenerating striated muscle and nerve fibers were judged unreactive for 5'-Nase. The epidermis and wound epithelium displayed negative responses for 5'-Nase. Cells forming the regeneration blastema were 5'-Nase reactive during the early formative phase, but with growth and development of the blastema into bulb and conic forms, these cells did not respond for this enzyme-activity. One suggestion offered is that the absence of 5'-Nase in cells of the blastema may be related to the lack of an adequate blood-vascular supply. Several functions of 5'-Nase in normal and regenerating tissues are discussed. A basic conclusion reached is that 5'-nucleotidase hydrolyses may be more involved in fundamental anabolic than in catabolic metabolism.