Uptake of topically applied 5-aminolevulinic acid and production of protoporphyrin IX in normal mouse skin: Dependence on skin temperature

The temperature dependence of the uptake phase of 5-aminolevulinic acid (AL A) and the following production phase of protoporphyrin IX (PpIX) in normal mouse skin was investigated. A cream containing 20% ALA was topically appl ied on the skin for 10 min. The amount of ALA-induced PpIX was evaluated by measuring the fluorescence of PpIX from the treated skin. No measurable am ount of PpIX was found in the skin immediately after 10 min application of ALA. The penetration of ALA into the skin was almost temperature independen t while the following production of PpIX was found to be a strongly tempera ture-dependent process, Practically no PpIX was formed in the skin as long as skin temperature was kept low (12 degrees C).