What is Ouabain?

Introduction

Ouabain is a heart glycoside and, in smaller doses, is utilized to treat hypotension as well as some arrhythmias. It does this by inhibiting Na/K-ATPase also called the sodium-potassium ion pump.

However, changes to the alpha-subunit Na+/K+-ATPase through amino acid substitutions are observed within specific species, specifically the herbivore-insect species which have led to resistance to toxins.

The substance is classified a highly dangerous chemical within the United States as defined in Section 302 of the U.S.

Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002) It is subject to stringent reporting requirements by all facilities that produce, store or utilize it in large quantities.

ouabain

Sources

Ouabain is located in the roots and stems, leaves as well as the seeds of Acokanthera Schimperi and Strophanthus graudus plants Both are indigenous to the eastern part of Africa.

Mechanism of action

Ouabain is a heart glycoside that works by inhibiting the Na+/K+-ATPase sodium potassium ion pump (but it’s not selective).

When ouabain is bound to the enzyme, it ceases to function, which leads to an increase in intracellular sodium.

This causes an increase in intracellular calcium. This leads to increased heart contractility and an increase in the cardiac vagal tone.

The changes in ionic gradients due to ouabain could alter the voltage of the membranes of cells, resulting in arrhythmias of the heart.

Signs and symptoms

A high dose of ouabain may be identified by the appearance of these symptoms such as rapid twitching of the chest and neck muscles respiratory distress, increased and irregular heartbeat, increase of blood pressure, convulsions wheezing and clicking, as well as gasping and rattling. Death can be caused by cardiac arrest.

Toxicology

Ouabain is a poisonous compound that has an LD50 at 5 mg/kg it is administered by mouth to rodents. However, the compound has a low bioavailability , and is not absorbed well from the digestive tract, as most of the oral dose is eliminated.

Injecting it intravenously results in higher available levels and has been demonstrated to lower in the LD50 by 2.2 mg/kg in rodents.

Following intravenous administration, effect begins to take effect in a matter of 2 to 10 minutes for humans with the greatest effect lasting over 1.5 hours.

Ouabain is eliminated via renal excretion. It is largely unaltered.

Biology-related impacts

Endogenous ouabain

In 1991, a particular sodium pump inhibitor that was high affinity that was indistinguishable from ouabain was identified in the human circulation and suggested to be one of the possible mediators of blood pressure, as well as the higher salt excretion in response to the loading of salt and volume.

The agent was a blocker of the sodium pump and was similar to digitalis.

Many different analytical methods resulted in the conclusion that the circulating chemical was called ouabain, and that humans produced this hormone in the form of an endogenous.

The majority members of scientific communities believed that the inhibitor was endogenous ouabain, and the evidence was convincing to suggest the fact that this molecule was produced within the adrenal gland.

A first speculation about the data from an analytical perspective resulted in the hypothesis that the endogenous ouabain could be the 11 epimer i.e. an isomer from plant ouabain.

But, this possibility was disproved by several methods such as the creation of 11 epimers as well as the proof that it has distinct chromatographic characteristics than ouabain.

The most important thing is that the first observations about the discovery orabain as a mammal was confirmed by a variety of tissues from three different continents using advanced analytical techniques which are described elsewhere.

Although there is a lot of evidence for this there were some who were skeptical about whether or not the endogenous substance was ouabain.

The argument was based less on solid analytical evidence, rather on the reality that immunoassays aren’t completely specific or reliable. Thus it was suggested that certain tests for endogenous orabain were able to detect different compounds or failed to detect or detect ouabain in any way.

Furthermore, it was proposed that rhamnose, which is the L-sugar component of ouabain, may not be synthesized in the body, despite research to contrary.

Another argument in favor of the existence of an endogenous source of ouabain was the absence of any effect of the rostafuroxin (a first-generation receptor for ouabain antagonist) on blood pressure in an unselected group that includes hypertensive sufferers.

Uses for medicine

While ouabain is not permitted for use in the USA and Canada, it is still used it is still used in France and Germany. Intravenous orabin is a well-established treatment for treatments for heart failure and some still advocate.

Its use orally and intravenously for angina pectoris and myocardial infarction in spite of its low and varied absorption.

The benefits of ouabain with respect to the prophylaxis or treatment of both conditions have been proven by numerous studies.

Animal usage of ouabain

The African crested rodent has a wide hairline with a white border covering a large area of an area of glandular skin along its flank.

If the animal is in danger or agitated, the hair on its back rises up and the flank strip separates open, showing the glandular part. Hairs on the flanks are extremely specific; at their edges they look like normal hairs, however they are soft, flexible, and absorptive.

Once the rat has chewed the tree instead of swallowing the poison, it applies the Masticate onto its specially-designed flank hairs, which are specially adapted to take in the toxic mix.

The result is a defense mechanism that can ill-affect the predators that try to take it in.

Synthesis

The complete synthesizing of ouabain was accomplished in 2008 by the Deslongchamps lab in Canada. The synthesis was carried out in the hope that polyanionic cycle (double Michael addition followed by aldol condensation) could lead to a tetracyclic tetracyclic intermediary with the expected function.

The figure below illustrates the main stages in the synthesis process of ouabain.

In their synthesis Zhang and co. from the Deslongchamps lab condensed cyclohexenone along with Nazarov substituent B during an inverse Michael addition to create tricycle C.

When the desired position was reached C decreased to aldehyde. It was protected from the alcohol by P-methoxybenzylether (PMB) to create the precursor to aldol needed to make D.

Following several steps it was possible to produce intermediate E. E had all the features and stereochemistry required to make ouabain. Its structure E was confirmed through comparison with ouabain, the product of degradation. Methylation of E which was catalyzed by Rhodium, created F.

Dehydroxylation and selective reduction that occurred in the second hydroxy groups of F resulted in G. G reacted with triphenyl phosphoranylidene ketones as well as the ester bonds of G were hydrolyzed, resulting in ouabagenin. It is a precursor for ouabain.

The glycosylation process of ouabagenin by rhamnose resulted in the production of ouabain.

Conclusions

In total, the current research has demonstrated that OUA treatment has anti-inflammatory and anti-apoptotic actions in the hippocampus that is afflicted by inflammation caused by LPS.

This effect is mediated by NF-kB activation, including in the neurogenesis-associated dentate gyrus. The ability of OUA to suppress the inflammatory process and maintain hippocampal BDNF levels in the face of inflammatory activity suggests that the NKA signaling cascade could be a new therapeutic target in neuroinflammation-associated disorders.

Na-K-ATPase (NKA) is a membrane protein vital to the survival of the living organism. It is found throughout the cells in the human body.

It has numerous functions, including the maintenance of the balance of osmotic equilibrium as well as. The volume of cells, their pH, and membrane potential.

This is accomplished through the hydrolysis of the adenosine triphosphate (ATP) molecules. Which results in the expulsion 3 sodium ions as well as the entry of potassium and sodium ions in cells.

Which is essential for neuronal excitability as well as the maintenance of cells.

Preparation of Proximal Tubule Primary Cells.

Rat tubule proximal (RPT) Cells were isolated from the kidneys of 20-day-old male rats, Sprague Dawley.

Cells were cultivated in a supplemented DMEM (20 MHEPES/24 M NaHCO3/10 mg/ml penicillin/10mg/ml streptomycin/10 percent FBS) on glass coverslips. In culture dishes for 48 hours in 5% CO2 at 37°C.

Cells were dehydrated for serum and then cultured in in the absence of antibiotics for 24 hours prior to the study.

Ratiometric Imaging.

Cells were treated with 3 mM of Fura-2/AM (Molecular Probes) for 1 hour in DMEM at 37°C for [Ca2+]i measurement in addition to 10 mM of SBFI/AM (Molecular Probes) for 2 hours in DMEM at 32°C for the intracellular concentration of sodium ([Na+]i) measurement.

Ratiometric imaging was carried out using the room heated (FCS2, Bioptechs, Butler, PA) mounted on an Zeiss. Axiovert 135 microscopy using the 40x/1.4 epifluorescence oil immersion objective.

The cells loaded with SBFI/AM and Fura-2/AM were activated at wavelengths of that was 340/10 nm or 380/10 nm. Emission fluorescence was captured using a 510/30-nm band-pass filter.

The data were recorded using an image intensifier system from GenIISys. That was connected to a camera CCD and analyzed with the acquisition software of Inovision.

Cells were activated at intervals of 30 seconds that is equivalent to an Nyquist time of 16.7 milliseconds.

All experiments were conducted using the P medium (100 mg NaCl/4 mM KCl/20 25 mM Hepes/25mM NaHCO3/1 mM CaCl2/1.2 1 mM MgCl2/1 10 mM NaH2PO4 M D-glucose). Nifedipine (Sigma) was used at 50 mM, 2-aminoethoxydiphenyl borate (Sigma) was used at 50 mM, jasplakinolide (JP, Molecular Probes) was used at 6 mM, 4-aminopyridine (Sigma) was used at 0.5 mM, and Bay K 8644 (Sigma) was used at 10 mM.

Power Spectrum Analysis.

Power spectrums of an audio signal is the ratio of the magnitude. That it receives from its Fourier transform, and is the sum of the contribution to a signal. That make up its components.

Utilizing MATLAB the oscillating part of a single cell’s measurement was removed to be centered. Centered, and trend corrected by computing Gauss ‘ least-square approximation, and then subtracting the trend from the data. Fast Fourier Transform was used to calculate the discrete Fourier transform.

The result is a spectrum in which the peaks correspond to different frequencies that are present on the initial data. It was identified using a comparison of the strength of the various peaks of the spectrum.

The power of the relative peak was determined by determining the size of the two extremes closest the peak. Then divided by the total size of the power spectrum.

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