Zebrafish Gills Could Explain Human Kidney Function

A study shows how the insights gained from zebrafish research could potentially impact the study of human kidney function.

AsianScientist (Mar. 7, 2014) – Researchers say that the discovery of how sodium ions pass through the gill of a zebrafish may be a clue to understanding a key function in the human kidney.

The gill is used in the fish as a transport system, retaining sodium ions (Na+) as nutrients and carrying away ammonium (NH4+) as waste. It is a key process allowing zebrafish to extract sodium ions from fresh water.

Researchers at the Tokyo Institute of Technology and Mayo Clinic have discovered a protein responsible for gas exchanges in the fish gill structure. Specifically, they studied and characterized the Na+/H+ (sodium/hydrogen) exchanger named NHE3, responsible for controlling the movement of sodium and hydrogen ions across the gill. The researchers directly demonstrated that NHE3 can function as a Na+/NH4+ exchanger.

In humans, NHE3 is involved in the acid-waste control system in the kidney, which requires the initial part of the kidney tubule to export ammonia/ammonium. It has always been assumed that NHE3 can perform a Na+/NH4+ exchange, but this has never been experimentally demonstrated.

In this case the protein allows the sodium ions to be absorbed from the forming urine while at the same time discarding waste from normally functioning cells, thus keeping the body in balance and serving as an energy saving system. The researchers say the same NHE3 protein performs a similar function in the intestine, pancreas, liver, lungs and reproductive system.

The researchers say their results in fish can be a clue or starting point for analyzing the process in people. They hope to continue their work in other species and ultimately further describe the process in humans.

“This is significant because the fish tends to mimic the process in humans,” says Michael Romero, an author of the study. “This is the true beauty of comparative physiology-– a lot of the organs function by very similar processes, down to ionic transfer.”

The article can be found at: Ito et al. (2014) Na+/H+ and Na+/NH4+ exchange activities of zebrafish NHE3b expressed in Xenopus oocytes.

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Source: Mayo Clinic; Photo: www.understandinganimalresearch.org.uk/Flickr/CC.

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