Fig. 3. Increased activity of CTSD after experimental skin injury. Acute disruption of the permeability barrier was induced by tape-stripping. Immediately after barrier disruption, pepstatin A or the carrier solution was applied and skin samples were obtained directly after tape-stripping (0 hours) or after 3 and 5 hours. CTSD activity was measured by specific parathyroid hormone (PTH) enzyme assays. The level of PTH protein was determined by western blotting using anti-PTH mAb (peptide 1-34). The amount of PTH in the assay at the starting point was used as a control and CTSD activity was calculated as the amount of PTH cleaved/hour.