New Study Suggests Ammonium Chloride Could Be the Sixth Basic Taste
Researchers at the USC Dornsife College of Letters, Arts, and Sciences have made an intriguing discovery that may revolutionize our understanding of taste. They have found evidence of a potential sixth basic taste related to the detection of ammonium chloride through the protein receptor OTOP1. This finding challenges the traditional notion of taste and its evolutionary significance.
While the well-known basic tastes include sweet, salty, sour, bitter, and umami, recent research proposes that the tongue might also have the ability to detect ammonium chloride as a distinct taste. The study, led by neuroscientist Emily Liman and her team, was published in the journal Nature Communications.
The concept of a sixth basic taste is not entirely new. Japanese scientist Kikunae Ikeda first proposed umami as a basic taste in the early 1900s, but it took nearly eighty years for the scientific community to officially acknowledge it. Now, scientists are suggesting that ammonium chloride might join the other five tastes as the sixth basic taste.
Ammonium chloride has long been known to evoke a strong response from the tongue. However, the specific receptors responsible for detecting it have remained elusive until now. Liman and her team discovered that the protein receptor OTOP1, which is responsible for sensing sour taste, also responds to ammonium chloride.
In laboratory experiments, the researchers introduced the Otop1 gene into human cells to produce the OTOP1 receptor protein. They exposed the cells to acid or ammonium chloride and observed their responses. The results showed that ammonium chloride strongly activates the OTOP1 channel, similar to or even better than acids.
To further confirm their findings, the team conducted experiments on mice. They found that mice with a functional OTOP1 protein found the taste of ammonium chloride unappealing and refused to drink the solution, while mice lacking the OTOP1 protein did not mind the taste, even at high concentrations. This behavioral response confirmed the essential role of the OTOP1 channel in detecting and reacting to ammonium.
The researchers also assessed the sensitivity of the OTOP1 channel to ammonium chloride in different species. They discovered variations in sensitivity, with chicken OTOP1 being more receptive to ammonium than zebrafish. These variations suggest that ecological differences between species may play a role in their sensitivity to ammonium.
Liman speculates that the ability to taste ammonium chloride may have evolved as a means to avoid consuming harmful substances with high concentrations of ammonium. Further research is needed to understand the evolutionary implications and explore the differences in sensitivity to ammonium among species.
The discovery of a potential sixth basic taste raises intriguing questions about the complexities of our sensory system and its evolutionary adaptation. The researchers hope to extend their studies to understand whether other members of the OTOP proton family, expressed in various parts of the body, also exhibit sensitivity to ammonium.
As scientists delve deeper into the intricacies of taste perception, ammonium chloride may soon join the ranks of other basic tastes. This groundbreaking research challenges our understanding of taste and opens a new realm of possibilities in the world of sensory perception.
Reference:
“The proton channel OTOP1 is a sensor for the taste of ammonium chloride” by Ziyu Liang, Courtney E. Wilson, Bochuan Teng, Sue C. Kinnamon and Emily R. Liman, 5 October 2023, Nature Communications.
DOI: 10.1038/s41467-023-41637-4
The study was funded by the National Institutes of Health.