New insights into salt transport in the kidney

August 23, 2012
The photo shows sections of a kidney from a claudin-10-deficient mouse and from a control mouse. Black staining (right) shows calcium deposits in the renal medulla, which are characteristic for nephrocalcinosis, a serious disease characterized by calcium deposits in the kidney.Credit: Photo: Tilman Breiderhoff/ Copyright: MDC

Sodium chloride, better known as salt, is vital for the organism, and the kidneys play a crucial role in the regulation of sodium balance. However, the underlying mechanisms of sodium balance are not yet completely understood. Researchers of the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch, Charité – Universitätsmedizin Berlin and the University of Kiel have now deciphered the function of a gene in the kidney and have thus gained new insights into this complex regulation process.

In humans, the kidneys filter around 1700 liters of blood every day, of which 180 liters are collected as primary urine and ultimately one to two liters of urine are excreted. The kidneys thus wash toxic waste products out of the body, but retain some useful substances and reintroduce them into the body, thus simultaneously regulating the and water balance.

Molecular velcro

In the study just published by Dr. Tilman Breiderhoff, Prof. Thomas Willnow (both MDC), as well as Dr. Nina Himmerkus and Prof. Markus Bleich (both of the University of Kiel) and Dr. Dominik Müller (Charité) the focus is on the claudin-10 gene, which is expressed in a specific segment of the kidney, in Henle's loop. In the thick ascending limb of this loop, , a large part of the filtered , as well as calcium and magnesium are reabsorbed. The under investigation, the claudin 10 protein, belongs to a family of proteins that connect the epithelial cells which cover the inner and outer surfaces of the body and stick them together like velcro. Claudins, however, also form pores, through which ions and substances are transported between the cells.

"If these transport processes are disturbed, this can lead to serious loss of function of the kidneys," Dr. Breiderhoff explained. As example he cited various human hereditary diseases in which either absorption of (Bartter syndrome) or of calcium and magnesium (familial hypomagnesemia with hypercalciuria and nephrocalcinosis – FHHNC) is disturbed. The second disease is characterized by a lack of magnesium in the blood and an excess of calcium in the urine, which leads to calcification of the kidneys. It is caused by mutations in one of two genes (claudin 16 or claudin 19), which also belong to the gene family of the claudins.

The researchers have now demonstrated in mice that the claudin-10 gene is involved in the reabsorption of salt in the kidney. If the gene in the kidney is deactivated, the reabsorption of sodium is impaired, but the reabsorption of calcium and magnesium is increased. The consequence is that the mice have elevated magnesium levels in the blood, and excess calcium is deposited in the kidney. Simultaneously, the urine volume is increased because the kidneys of the mice cannot reabsorb enough water, a sign that the recovery of salt is disturbed.

Explore further: Kidney stone mystery solved

More information: PNAS Early Edition, doi/10.1073/pnas.1203834109

Related Stories

Kidney stone mystery solved

April 18, 2012
Kidney stones strike an estimated 1 million Americans each year, and those who have experienced the excruciating pain say it is among the worst known to man (or woman).

Diets high in salt could deplete calcium in the body: research

July 24, 2012
The scientific community has always wanted to know why people who eat high-salt diets are prone to developing medical problems such as kidney stones and osteoporosis.

Kidney damage and high blood pressure

September 22, 2011
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 ...

Abnormal activation of a protein may explain deadly link between high salt intake and obesity

September 19, 2011
Dietary salt intake and obesity are two important risk factors in the development of high blood pressure. Each packs its own punch, but when combined, they deliver more damage to the heart and kidneys than the sum of their ...

Recommended for you

Google searches can be used to track dengue in underdeveloped countries

July 20, 2017
An analytical tool that combines Google search data with government-provided clinical data can quickly and accurately track dengue fever in less-developed countries, according to new research published in PLOS Computational ...

MRSA emerged years before methicillin was even discovered

July 19, 2017
Methicillin resistant Staphylococcus aureus (MRSA) emerged long before the introduction of the antibiotic methicillin into clinical practice, according to a study published in the open access journal Genome Biology. It was ...

New test distinguishes Zika from similar viral infections

July 18, 2017
A new test is the best-to-date in differentiating Zika virus infections from infections caused by similar viruses. The antibody-based assay, developed by researchers at UC Berkeley and Humabs BioMed, a private biotechnology ...

'Superbugs' study reveals complex picture of E. coli bloodstream infections

July 18, 2017
The first large-scale genetic study of Escherichia coli (E. coli) cultured from patients with bloodstream infections in England showed that drug resistant 'superbugs' are not always out-competing other strains. Research by ...

Ebola virus can persist in monkeys that survived disease, even after symptoms disappear

July 17, 2017
Ebola virus infection can be detected in rhesus monkeys that survive the disease and no longer show symptoms, according to research published by Army scientists in today's online edition of the journal Nature Microbiology. ...

Mountain gorillas have herpes virus similar to that found in humans

July 13, 2017
Scientists from the University of California, Davis, have detected a herpes virus in wild mountain gorillas that is very similar to the Epstein-Barr virus in humans, according to a study published today in the journal Scientific ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.