Ouabain

Ouabain (100 nM) inhibits ATPase activities with 25%. ^[1] 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. ^[2] 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. ^[3] 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. ^[4]

Ouabain (14.4 mg/kg.d s.c. intermittent) further increases total peripheral resistance (TPR) in rats with heart failure due to myocardial infarction (MI), while continuous Ouabain treatment normalized TPR in rats. Ouabain (14.4 mg/kg.d s.c. continuous) significantly improves basal and maximal CO (basal: 83 mL/min; maximal: 134 mL/min). ^[5]