image: This is Dr. Clint Makino of the Makino Laboratory at Mass. Eye and Ear, Harvard Medical School. view more
Credit: Mass. Eye and Ear
Bicarbonate (baking soda) makes sparkling water sparkle, causes bread to rise, absorbs odors and can be used for cleaning all sorts of stuff, including your teeth. In the body, it plays essential roles in buffering pH, aiding in digestion and neutralizing lactic acid produced during physical exertion. Much of the bicarbonate in our bodies comes from carbon dioxide, which is produced as a waste product in all cells, although some is ingested with carbonated beverages and certain types of foods.
Now a new study from the Makino Laboratory at Massachusetts Eye and Ear/Harvard Medical School and colleagues at Salus University, describes how bicarbonate also alters how we see by modifying the visual signal generated by rod and cone photoreceptors that detect light. This study is described online in the Journal of Biological Chemistry.
Within rods and cones, a small soluble molecule, cGMP, links photon absorption to the electrical activity of the photoreceptor. In the light, cGMP is destroyed and ion channels are closed. Positively charged sodium ions cease to enter the rod or cone and the membrane potential becomes more negative or hyperpolarized. Bicarbonate directly stimulates an enzyme called guanylate cyclase that synthesizes cGMP.
"By opposing the effect of light, bicarbonate limits the size of the photon response and quickens its recovery. As a result, sensitivity to light is slightly lower but our ability to track moving objects is improved," said lead author Clint Makino, Ph.D., director of the Makino Laboratory at Mass. Eye and Ear and an Associate Professor of Ophthalmology at Harvard Medical School. "An intriguing implication is that vision may change with metabolic state, although further research is necessary for confirmation. It is now known that in some types of retinal diseases, a genetic defect causes cGMP in the rods and/or cones to rise to abnormally high, lethal levels. Once lost, rods and cones are not replaced, so an irreversible blindness is the tragic outcome."
In the future, scientists in the Makino Laboratory want to investigate the possibility that controlling bicarbonate levels in the eye will slow the progress of, or may even prevent, eye diseases.
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This study was supported by NIH EY011358, EY014104, EY023980, Research to Prevent Blindness, and the Howe Laboratory Endowment of the Massachusetts Eye and Ear.
The paper is entitled: Bicarbonate Modulates Photoreceptor Guanylate Cyclase (ROS-GC) Catalytic Activity J. Biol. Chem. published March 12, 2015 as doi:10.1074/jbc.M115.650408. http://www.jbc.org/content/early/2015/03/12/jbc.M115.650408.full.pdf+html
Researchers: Teresa Duda, Xiao-Hong Wen, Tomoki Isayama, Rameshwar K. Sharma and Clint L. Makino.
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Mass. Eye and Ear clinicians and scientists are driven by a mission to find cures for blindness, deafness, and diseases of the head and neck. After uniting with Schepens Eye Research Institute in 2011, Mass. Eye and Ear in Boston became the world's largest vision and hearing research center, offering hope and healing to patients everywhere through discovery and innovation. Mass. Eye and Ear is a Harvard Medical School teaching hospital that trains future medical leaders in ophthalmology and otolaryngology, through residency as well as clinical and research fellowships. Internationally acclaimed since its founding in 1824, Mass. Eye and Ear employs full-time, board-certified physicians who offer high-quality and affordable specialty care that ranges from the routine to the very complex. U.S. News & World Report's "Best Hospitals Survey" has consistently ranked the Mass. Eye and Ear Departments of Otolaryngology and Ophthalmology among the top hospitals in the nation. For more information about life-changing care and research, or to learn how you can help, please visit MassEyeAndEar.org.
Journal
Biological Chemistry