In vitro activity: Ouabain (100 nM) inhibits ATPase activities with 25%. Ouabain (0.1 μM-1.0 μM) inhibits the Na+ pump and increases stored Ca2+ in cultured rat astrocytes. High Ouabain affinity isoforms (alpha2 in astrocytes, alpha3 in neurons and myocytes) are confined to a reticular distribution within the PM that paralleled underlying endoplasmic or sarcoplasmic reticulum. Ouabain (0.5-1.0 mM) increases the levels of alpha1 and beta1 mRNAs, whereas it decreases those of alpha2 and beta2 mRNAs in cultured rat astrocytes. Ouabain increases alpha1 and beta1, but not alpha2 and beta2, proteins, and that the isoforms in control and ouabain-treated cultures. The ouabain-induced increase in alpha1 mRNA is blocked by cycloheximide (10 mM), the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester (30 mM), and FK506 (1 nM) in cultured rat astrocytes. Ouabain (10 μM) induces significant PMD in both cell lines (28.1% of MDCK cells and 47.9% of Ma104 cells are gated in region M1, against 11.8% and 14.6% of the respective controls), but unexpectedly this effect is more remarkable in Ma104 cells. Ouabain (10 μM) induces a sustained increase in P-Tyr in MDCK cells and GSH almost completely reverted this effect, while the effect is not significant in Ma104 cells.

Kinase Assay: Ouabain Octahydrate is a Na(+)/K(+) ATPase inhibitor. Ouabain (100 nM) inhibits ATPase activities with 25%. Ouabain (0.1 μM-1.0 μM) inhibits the Na+ pump and increases stored Ca2+ in cultured rat astrocytes. High Ouabain affinity isoforms (alpha2 in astrocytes, alpha3 in neurons and myocytes) are confined to a reticular distribution within the PM that paralleled underlying endoplasmic or sarcoplasmic reticulum. Ouabain (0.5-1.0 mM) increases the levels of alpha1 and beta1 mRNAs, whereas it decreases those of alpha2 and beta2 mRNAs in cultured rat astrocytes. Ouabain increases alpha1 and beta1, but not alpha2 and beta2, proteins, and that the isoforms in control and ouabain-treated cultures. The ouabain-induced increase in alpha1 mRNA is blocked by cycloheximide (10 mM), the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester (30 mM), and FK506 (1 nM) in cultured rat astrocytes.

Cell Assay: Cell viability is determined using a Cell Counting Kit-8 assay. Briefly, 100 μL Raji cells (5×104/mL) are seeded in triplicate in a 96-well plate and treated with various concentrations of ouabain (400, 200, 100, 50, 25, 12.5, 6.25, 3.13, 1.56, 0.78 and 0.39 nM) for 48 h. Following the 48-h treatment, 10 μL CCK-8 reagent is added to each well, and the cells are incubated for an additional 3 h at 37°C. Optical density (OD) values at 450 nm are subsequently measured, and each ouabain concentration is assessed in triplicate. Raji cells cultured in medium without drug served as controls. Cell viability is calculated according to the following formula: Inhibition rate (%)=[1 – (OD450(sample) – OD450(blank))/(OD450(control) – OD450(blank))] × 100.