Harvard: Bicarbonate, a key ingredient in baking soda, makes sparkling water
sparkle, causes bread to rise, absorbs odors and can be used to clean
all sorts of stuff, including your teeth. It’s also an important
naturally occurring compound in the body, where 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 led by Harvard Medical School researchers in the
Makino Laboratory at Massachusetts Eye and Ear and HMS and conducted
with 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.
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Within rods and cones, a small soluble molecule known as 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,
HMS associate professor of ophthalmology and director of the Makino
Laboratory. “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.
This study was supported by NIH grants EY011358, EY014104 and
EY023980; Research to Prevent Blindness and the Howe Laboratory
Endowment of Mass Eye and Ear.
Adapted from a Mass Eye and Ear news release.