Enzyme-independent NO stores in human skin: quantification and influence of UV radiation.

Nitric oxide (NO) has many functions in the skin, including the mediation of inflammation and antimicrobial defense, wound healing, regulation of keratinocyte homeostasis, and regulation of apoptosis following UV radiation. NO is synthesized by a family of NO synthase enzymes, but its rapid release following UV exposure suggests the existence of preformed stores. NO can be converted into nitrite or nitrosothiols that are stable until cleaved by UV to release NO.