The salivary gland secretes saliva that helps us chew and swallow the food we eat. The pancreas secretes digestive juices that enable our bodies to break down the fat, protein, and carbohydrates in the food. Secretions like these are important in countless activities that keep our bodies running day and night. A study published in the journal Science Signaling uncovers a previously mysterious process that makes these secretions possible.

At the heart of the new study is calcium, which is present in all of our cells and is a gatekeeper of sorts: an increase in calcium in our cells opens up “gates” or “channels” that are required for the production and secretion of fluids like saliva. If calcium doesn’t increase inside cells the gates won’t open, a problem that occurs in diseases like Sjögren’s syndrome. Sjögren’s patients experience dry mouth due to a lack of saliva and have difficulty chewing, swallowing, and speaking, which severely hampers quality of life.

Scientists have known that the presence of a protein called the IP₃receptor is necessary to increase calcium and generate channels in many, if not all, cells. But, the IP₃ receptor is complex: one channel is created from four identical units in the IP₃ receptor, and it was not known how many of the individual units had to be engaged for the channel to work.

Using advanced molecular engineering and gene editing techniques the team discovered that, without exception, all four parts must be activated (turned on) for calcium to increase in a cell and start processes like fluid secretion.

Researchers believe this feature ensures that the calcium channel only opens under strict conditions that result in secretions, avoiding harmful events that would occur if the channel could open more easily. (Paradoxically, too much calcium is also bad and can lead to processes that kill cells. So, it is no surprise that cells keep tight control over calcium levels.)

https://www.urmc.rochester.edu/news/story/4538/study-the-science-behind-bodily-secretions.aspx