Related Experiment Video
Updated: Dec 17, 2025
Optimization of the Epimedii Folium Mutton-Oil Processing Technology and Testing Its Effect on Zebrafish Embryonic Development
Published on: March 17, 2023
Ouabain and Marinobufagenin: Physiological Effects on Human Epithelial and Endothelial Cells
E A Klimanova1, D A Fedorov2, S V Sidorenko2
1Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia. klimanova.ea@yandex.ru.
Abstract:
Long-term study on the identification of Na,K-ATPase endogenous inhibitors in mammalian tissues has resulted in the discovery of ouabain, marinobufagenin (MBG), and other cardiotonic steroids (CTS) in the blood plasma. Production of ouabain and MBG is increased in essential hypertension and other diseases associated with hypervolemia. Here, we compared the effects of ouabain and MBG on the Na,K-ATPase activity (measured as the transport of Na+, K+, and Rb+ ions) and proliferation and death of human renal epithelial cells (HRECs) and human umbilical vein endothelial cells (HUVEC) expressing α1-Na,K-ATPase. Ouabain concentration that provided the half-maximal inhibition of the Rb+ influx (IC50) into HRECs and HUVECs was 0.07 μM. In both types of cells, the IC50 values for MBG were 10 times higher than for ouabain. Incubation of HREC and HUVEC with 0.001-0.01 μM ouabain for 30 h resulted in 40% increase in the [3H]thymidine incorporation into DNA; further elevation of ouabain concentration to 0.1 μM completely suppressed DNA synthesis. MBG at the concentration of 0.1 μM activated DNA synthesis by 25% in HRECs, but not in HUVECs; 1 μM MBG completely inhibited DNA synthesis in HRECs and by 50% in HUVECs. In contrast to HRECs, incubation of HUVECs in the serum-free medium induced apoptosis, which was almost completely suppressed by ouabain and MBG at the concentrations of 0.1 and 3 μM, respectively. Based on these data, we can conclude that (i) the effect of MBG at the concentrations detected in the blood plasma (<0.01 μM) on HRECs and HUVECs was not due to the changes in the [Na+]i/[K+]i ratio; (ii) the effect of physiological concentrations of ouabain on these cells might be mediated by the activation of Na,K-ATPase, leading to cell proliferation.
Insights
Cardiotonic steroids like ouabain and marinobufagenin (MBG) affect cell growth and death. Ouabain at physiological levels may activate Na,K-ATPase, promoting cell proliferation in renal and endothelial cells.
Area of Science:
- Biochemistry
- Cell Biology
- Cardiovascular Research
Background:
- Endogenous cardiotonic steroids (CTS), including ouabain and marinobufagenin (MBG), are found in mammalian plasma.
- Elevated ouabain and MBG levels are observed in conditions like essential hypertension and hypervolemia.
- The specific cellular effects of these CTS on Na,K-ATPase activity, proliferation, and apoptosis require detailed investigation.
Purpose of the Study:
- To compare the effects of ouabain and MBG on Na,K-ATPase activity, cell proliferation, and cell death.
- To investigate these effects in human renal epithelial cells (HRECs) and human umbilical vein endothelial cells (HUVECs) expressing α1-Na,K-ATPase.
- To elucidate the mechanisms underlying CTS actions at physiologically relevant concentrations.
Main Methods:
- Measurement of Na,K-ATPase activity via ion transport (Na+, K+, Rb+).
- Assessment of cell proliferation using [3H]thymidine incorporation into DNA.
- Induction and assessment of apoptosis in HUVECs under serum-free conditions.
Main Results:
- Ouabain showed significantly higher inhibition of Rb+ influx (IC50 = 0.07 μM) compared to MBG in both HRECs and HUVECs.
- Low concentrations of ouabain (0.001-0.01 μM) increased DNA synthesis in HRECs and HUVECs, while higher concentrations suppressed it.
- MBG demonstrated dose-dependent effects on DNA synthesis, activating it at 0.1 μM in HRECs and inhibiting it at higher concentrations in both cell types; both CTS suppressed apoptosis in HUVECs.
Conclusions:
- At plasma concentrations (<0.01 μM), MBG's effects on HRECs and HUVECs are not mediated by changes in intracellular Na+/K+ ratio.
- Physiological concentrations of ouabain may stimulate cell proliferation in HRECs and HUVECs through Na,K-ATPase activation.
- Ouabain and MBG exhibit distinct yet overlapping roles in regulating cell proliferation and survival, with potential implications for cardiovascular diseases.
Related Concept Videos
01:24Regulation of Angiogenesis and Blood Supply
01:21Paracrine Signaling
01:17Hormonal Regulation of Blood Pressure
Epinephrine and Norepinephrine
The adrenal medulla releases epinephrine and norepinephrine, catecholamines that enhance and extend the sympathetic or "fight or flight" physiological response. These hormones escalate heart rate and the force of contraction...