Comparison of cathepsin L activity in cheek and forearm stratum corneum in young female adults

Purpose The objective is to determine the usefulness of cathepsin L (Cat L) activity derived from the stratum corneum as an index of skin conditions by comparing the cheek and the forearm, in 20 female young adults. Methods The sebum quantity, hydration index, melanin index and pH were measured with a sensor system consisting of a sebumeter, a corneometer, a mexameter and a pH meter. The stratum corneum was collected using tape stripping. Cat L and total protein (TP) were analyzed and the Cat L/TP ratio was calculated. Results Our results indicated that (i) chronic sun exposure causes an increase in Cat L activity; and (ii) in order to cancel out the influence of the collecting technique, it is very important to measure the Cat L/TP ratio. Conclusion It is considered that the Cat L/TP ratio may be a useful index of the skin conditions in humans.