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Dexamethasone induced expression of phosphatase inhibits generation of reactive oxygen species in ehrlich ascietes tumor cells
Author(s) -
Salimath Bharathi P.,
Sharma Ranjana,
Tabassum Arshia
Publication year - 1998
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216549800204082
Subject(s) - reactive oxygen species , dexamethasone , chemistry , phosphatase , microbiology and biotechnology , biochemistry , cancer research , biology , enzyme , endocrinology
Both pre‐activated and phorbol ester tetradecanoyl phorbol myristate acetate (TPA) activated reactive oxygen species (ROS) generation were inhibited by dexamethasone in viva. Time kinetics on influence of dexamethasone on cytosolic phosphoprotein phosphatase activity revealed that, when compared to phosphatase activity in cytosol of control Ehrlich ascites tumor (EAT) cells, a 5‐fold increase in specific activity is seen in the cytosol of EAT cells treated (in viva, 0‐90 min. 1 mg/kg body weight) with dexamethasone. Dexamethasone induced phosphatase was partially purified by conventional ion‐exchange and gel filtration column chromatographic techniques. Purified phosphatase had a molecular weight of 70 KDa by SDS‐PAGE. A dose‐dependent inhibition of TPA activated ROS generation by partially purified phosphatase in permeabilized EAT cells suggested that dephosphorylation is a major regulatory mechanism in “switching off” of the respiratory burst. Anti‐phosphatase antibodies were raised, purified and were used to quantitate cytosolic phosphatase by ELISA, which revealed that dexamethasone induces 6‐fold increase in expression of phosphatase in EAT cells by 120 min. The expression of phosphatase in EAT cell cytosol gas further confirmed by immunostaining using anti‐phosphatase antibodies, the results of which showed intense blue staining on development with BCIP/NBT.