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article imageHormone Found in Human Urine Could be High Blood Pressure Treatment

By Bob Ewing     Nov 8, 2007 in Science
For more than 40 years, researchers have suspected there must be a natural hormone that could safely flush sodium out of the body and could be harnessed to develop more effective and safer treatments for high blood pressure, or hypertension.
Researchers have suspected that there existed a natural hormone that could safely flush sodium out of the body and that furthermore, this hormone could be used to develop effective and safer treatments for hypertension or high blood pressure.
The drugs that are currently being used to lower sodium levels all have the same serious side effect they reduce potassium levels.
A research team composed of scientists from Cornell University and the Boyce Thompson Institute for Plant Research (BTI) have used a new technique and identified a hormone from human urine.
This hormone is a xanthurenic-acid derivative and it seems able to do the job. The discovery opens the door to developing novel medications to control sodium levels and treat hypertension.
Frank Schroeder who is an assistant scientist at BTI and co-author of the paper had developed a technique that would analyze complex mixtures of small molecules, thus making it possible to finally identify the hormone.
Researchers already were aware that human steroid called aldosterone activates the kidney to reabsorb sodium and excrete potassium. This knowledge led them to suspect that there must be another hormone that would trigger the kidney to do the opposite: excrete sodium and reabsorb potassium.
A number of previous attempts have been made to find such a hormone in human urine, but as urine contains a mix of hundreds of molecules, it was therefore not possible to isolate the correct one, probably because the suspected hormone breaks down easily during traditional chemical analysis.
The efforts to find this “holy grail” of kidney hormones had been largely abandoned until 2003 when a private company, Naturon Corp., contacted Schroeder.
Schroeder developed an approach that was based on nuclear magnetic resonance (NMR) spectroscopy of partially purified urine. Chemists use NMR to determine the structures of unknown compounds, has only been used for the analysis of purified compounds.
The approach that Schroeder employed allowed NMR to identify compounds without isolating them, for example in a complex mixture such as partially fractionated urine. As a result, three completely new compounds were revealed.
Each of the new compounds was subsequently synthesized and injected into rats. The rats' urine was then monitored.
Two of the identified compounds are derivatives of a common metabolite xanthurenic-acid and raised sodium levels in the rat's urine but kept potassium levels constant. According to Schroeder aldosterone is a steroid hormone, which does the opposite, however, this newly discovered molecule is structurally more similar to such amino acid-derived neurotransmitters as dopamine and serotonin and, therefore, may also play other roles in the body.
"Now, we want to know what other functions these compounds have and whether they directly influence blood pressure," said Schroeder.
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