Now, Dr. Stefan Lechner and Professor Gary R. Lewin of the Max Delbrück Center (MDC) Berlin, Professor Friedrich C. Luft of the Experimental and Clinical Research Center (ECRC) of MDC and Charité and Professor Jens Jordan (ECRC; now Hannover Medical School, MHH) have discovered a new group of sensory neurons in the mouse liver which mediates the regulation of blood pressure and metabolism. This control center outside of the brain is triggered simply by drinking water and leads to an elevation of blood pressure in sick and elderly people. (Neuron, No. 69, 332-344)*.
More than ten years ago Professor Jens Jordan, MD, then a research fellow at Vanderbilt University in Nashville, Tennessee, observed a phenomenon together with his colleagues, more or less by accident. Later, at the former Franz Volhard Clinic of the Charité in Berlin-Buch, Jens Jordan again observed that in patients with a damaged nervous system, blood pressure readings rose by as much as 50 mm Hg if the patients drank a half liter of water all at once. “In young people whose sympathetic nervous system was stimulated by drugs, water intake also caused blood pressure levels to rise,” said Professor Friedrich C. Luft of the ECRC. “Even in healthy older people, water drinking triggers a regulator for blood pressure.” The two clinicians invited neuroscientists at MDC to collaborate with them and started a joint research project.
For 60 years researchers have suspected that there must also be a control center for the body’s self-regulation located outside of the brain. Motivated by findings of recent studies, the researchers in Berlin-Buch therefore looked for sensory neurons specifically in organs peripheral to the central nervous system that would detect body changes caused by water intake and would thus be able to activate a regulator which in old and sick people causes blood pressure to rise and which stimulates metabolism in healthy young people.
“In this entire process, osmolality plays a key role,” explained Dr. Stefan Lechner, a member of Professor Lewin’s research group. “It is the measure of the body’s water balance. And it indicates how many molecules are dissolved in a liter of fluid. Each species has a characteristic set point for osmolality, which depends to a great extent on the immediate living conditions. We wanted to know how deviations of osmolality are able to activate a regulator.”
The researchers observed in the mouse model that specific neurons in the liver react actively to water intake. The water the mice drink is absorbed in the small intestine and reaches the blood system via the liver. Due to the sudden water intake, the osmolality in the blood vessels of the liver falls under its set-point value. This deviation is registered by sensory neurons in the liver, the so-called osmoreceptors, as the researchers could now demonstrate. They found that the osmoreceptors transform the information into an electrical signal, which in turn triggers a reflex and stimulates the hepatic blood vessels to raise blood pressure.Ion Currents Help to Elucidate the Mechanisms
“The TRPV4 ion channel opens in just a few hundred milliseconds like the lens of a camera, letting the electrical signal through and thus activating a regulator,” explained Dr. Stefan Lechner. “We were now interested in whether the TRPV4 ion channel is acting alone or whether it needs subunits to aid it, and we wanted to know how the whole thing works mechanically.”
In further experiments, to elucidate the role and function of TRPV4 in this regulation process, the researchers studied mice in which the gene for the TRPV4 ion channel had been inactivated. After giving these knockout mice water to drink, they did not observe any activation of the osmoreceptors in the liver. No ion currents flowed and as a consequence, no reflex was triggered. The researchers concluded that the elevation of the blood pressure due to water intake must be associated with the presence of the TRPV4 ion channel.Consequences for therapy
“The effect of drinking water on blood pressure regulation is already leading to therapeutic consequences in the daily routine of the hospital,” Professor Jordan added. "We tell patients to drink water who, due to blood pressure regulation disorders, suffer from fainting attacks when standing. This alleviates the symptoms and at the same time we are able to reduce the amount of medication. Healthy people can also suffer fainting attacks when they stand for a long time or are otherwise under strain, e.g. when they donate blood. In many cases these can be avoided by drinking water. Our decade-long persistence in investigating osmolalic self-regulation has really paid off!”* The molecular and cellular identity of peripheral osmoreceptors
5Experimental and Clinical Research Center (ECRC), Charité Campus Buch, 13125 Berlin, GermanyBarbara Bachtler
Barbara Bachtler | Max-Delbrück-Centrum
Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care
Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses