Nuclear localization and characterization of alkaline phosphatase in neutrophils from normal controls and pregnant women

Abstract

There were controversial data concerning localization of alkaline phosphatase (AP) in neutrophil nuclei under physiological conditions. In this context, the AP pattern has been determined on nuclei preparations from normal human neutrophils. Blood cells were isolated from 10 healthy adults and from 3 women in the third trimester of an uncomplicated pregnancy. Purity of nuclear suspension was checked by electron microscopy and assay of organelle marker enzymes. Electron microscope cytochemistry and immunocytochemistry studies were carried out on WBC. Enzyme characterization was performed by the usual biochemical procedures. AP was found in nuclear preparations from four of ten normal controls. When present, AP was detected in approximately two-thirds of the nuclei examined, representing an average of 20% of the total cell activity. Conversely, a large amount of nucleus-bound enzyme (55% of total AP activity) was recognized in all pregnant women samples. Biochemical and immunological characteristics clearly differentiate AP forms in the two groups of subjects. Normal controls have an heterogeneous enzyme pattern. AP positive preparations contain a mixture of isoenzymes: a prominent heat labile form and a relatively heat stable minor component. The heat stable fraction displays some properties similar to those previously described in leukocyte AP. Pregnant women express a unique very heat labile isoenzyme identical in its main characteristics to the early placental type.

Sialidase Activity in Nuclear Membranes of Rat Brain

“…This result, however, cannot be taken as an indication for a high degree of contamination by plasma membranes. Earlier studies have demonstrated the presence of alkaline phosphatase activity in nuclear membranes from rat astrocytes and oligodendrocytes (Mori and Nagano, 1985a,b) and human leukocytes (Vergnes et al, 1992). It is known that this nonspecific phosphohydrolase can hydrolyze various phosphomonoester compounds, including 5 '-AMP, at a wide pH range.…”

Improving Sensitivity of the Electrophoretic Mobility Shift Assay by Restricting Tissue Phosphatase Activities

“…Most of the phosphatase activity is localized to the cytoplasm, yet a substantial portion of these enzymes (which also comprises AP) has been found in cell nuclei (9,18,19). This explains why most nuclear extracts get contaminated by these enzymes in the course of their preparation.…”