Role of iodine in the tear glands

Salivary and Lacrimal Glands

Areas such as the eye and the mouth are repeatedly exposed to infectious organisms. The fact that these areas are not frequent victims of infection speaks to a complex system of immunological protection in these areas. These tissues employ not only antibodies, but also the use of small mol­ecules with antimicrobial properties. Iodine and iodine-containing compounds likely play an important role in protecting the body against infection. As has been discussed previously, through the action of various enzymes iodine can form a number of active compounds important for fighting disease. In the presence of a peroxidase such as lactoperoxidase, and hydrogen peroxide, iodide is activated to hypoiodous acid (HI), which is a potent antimicro­bial. In addition, unincorporated iodine itself is an impor­tant disinfecting agent.
Studies employing immunohistochemistry on tissues from salivary and lacrimal glands have demonstrated the presence of the symporter (Spirzweg et 4., 1999; Thiang et al„ 1998)- To date, there appear to be no iodine uptake studies in lacrimal tissue. in addition, the mechanism con­trolling NIS expression there remains to be understood. Given the importance of having proper immunological defense of these areas, it is reasonable to hypothesize that the symporter may be constitutively expressed. It is also possible that in the salivary and lacrimal glands, syin­porter expression falls under the control of inflammatory crokincs. Such a system would seem consistent with the antimicrobial function iodine appears Co be playing in these tissues.