Kidney damage and high blood pressure

The kidney performs several vital functions. It filters blood, removes waste products from the body, balances the body's fluids, and releases hormones that regulate blood pressure. A number of diseases and conditions can damage the kidney's filtration apparatus, such as diabetes and immune disorders. This damage leads to a condition called nephrotic syndrome, which is characterized by protein in the urine, high cholesterol and triglycerides, and swelling (edema). People with nephrotic syndrome retain salt and water in their bodies and develop swelling and high blood pressure as a result.

Scientists have now begun to understand on a cellular level and how the activity of certain molecules in damaged kidneys contributes to salt and water retention in nephrotic syndrome. Several new insights in this area of research will be presented at the7th International Symposium on Aldosterone and the ENaC/Degenerin Family of , being held September 18-22 in Pacific Grove, Calif. The meeting is sponsored by the .

Faulty Filtration

The kidneys are marvels of filtration, processing roughly 150 to 200 quarts of blood each day through called nephrons. There are about 1 million nephrons per kidney, and each nephron consists of a filtering unit of blood vessels called a glomerulus, which is attached to a tubule. Filtered blood enters the tubule, where various substances are either added to or removed from the filtrate as necessary, and most of the filtered sodium and water is removed. The filtrate that exits the tubule is excreted as urine.

In nephrotic syndrome, a damaged filtration barrier allows substances that are not normally filtered to appear in the filtrate. One of these substances is the protein plasminogen, which is converted in kidney tubules to the protease plasmin. In their research, Thomas R. Kleyman, Professor of Medicine and of and Physiology at the University of Pittsburgh School of Medicine and the Symposium's co-organizer, and Ole Skøtt, Professor of Physiology and Pharmacology and Dean at the University of Southern Denmark in Odense, independently found that plasmin plays a role in activating the epithelial sodium channel (ENaC) on cells in the . ENaC is a protein embedded in cell membranes that facilitates the absorption of filtered sodium from tubules. When ENaC is becomes overactive, excessive absorption of filtered sodium may lead to sodium and water retention.

According to Dr. Kleyman, these findings provide an explanation of how damage to the glomeruli in the kidney's nephrons leads to edema and . Dr. Kleyman explains: "When plasminogen is cleaved, it can act on several targets. One of those targets is ENaC. Another is the protein prostasin, which, once cleaved, will activate ENaC, as well."

Dr. Kleyman noted the implications these findings have for treating edema and high blood pressure in patients suffering from nephrotic syndrome. "This is important because if plasmin activates ENaC, it suggests that targeting ENaC in the kidneys with ENaC inhibitors may be a treatment option."

More information: Dr. Skøtt will discuss the Danish team's research in his presentation, "Plasmin, ENaC, and Nephrotic Syndrome," on Thursday, Sept. 22. Ossama B. Kashlan, Research Assistant Professor of Medicine in the Renal-Electrolyte Division at the University of Pittsburgh, will discuss the molecular mechanisms by which proteases activate ENaC in his presentation, "Conformational Trapping of the Closed State of ENaC" on Monday, Sept. 19.

add to favorites email to friend print save as pdf

Related Stories

Opening a channel for salt retention

Apr 25, 2008

A research team has developed the first small molecule that can reversibly activate a key protein involved in balancing sodium levels, paving the way for drugs that can treat low blood pressure and related conditions.

Recommended for you

World 'losing the battle' to contain Ebola: MSF

10 seconds ago

International medical agency Medecins sans Frontieres said Tuesday the world was "losing the battle" to contain Ebola and called for a global biological disaster response to get aid and personnel to west Africa.

Mutating Ebola viruses not as scary as evolving ones

30 minutes ago

My social media accounts today are cluttered with stories about "mutating" Ebola viruses. The usually excellent ScienceAlert, for example, rather breathlessly informs us "The Ebola virus is mutating faster in humans than in animal hosts ...

War between bacteria and phages benefits humans

1 hour ago

In the battle between our immune systems and cholera bacteria, humans may have an unknown ally in bacteria-killing viruses known as phages. In a new study, researchers from Tufts University, Massachusetts ...

Ebola kills 31 people in DR Congo: WHO

3 hours ago

An outbreak of the Ebola virus in the Democratic Republic of Congo has killed 31 people and the epidemic remains contained in a remote northwestern region, UN the World Health Organization (WHO) said Tuesday.

Dengue fever strikes models in Japan

5 hours ago

A worsening outbreak of dengue fever in Japan has claimed its first celebrities—two young models sent on assignment to the Tokyo park believed to be its source.

Japanese researchers develop 30-minute Ebola test

5 hours ago

Japanese researchers said Tuesday they had developed a new method to detect the presence of the Ebola virus in 30 minutes, with technology that could allow doctors to quickly diagnose infection.

User comments