Water permeation barrier in isolated cutaneous newborn rat epidermis

Abnormal water barrier function occurs in irritated skin and certain cutaneous diseases. Methods have been compared for separating the epidermis (site of the barrier) from the whole skin without disturbing the barrier function. The epidermis was separated from newborn rat skin by (1) exposure to 10% trypsin at 4 degrees C for 16 h, (2) exposure to 0.2% dispase at 4 degrees C for 16 h, (3) heating for 50 s at 55 degrees C, (4) or heating for 40 s at 50 degrees C after the whole skin was kept in medium at the air-liquid interface for 1 day at 35 degrees C. Water permeation of the isolated epidermis was then measured immediately or after 3, 5, 8, and 10 days of maintenance at the air-liquid interface. The water permeation barrier constant (kp) was 1.9+/-0.9 cm/h in intact rat skin. At 0 day of maintenance, the kp of the epidermis was 2.1+/-0.9 after treatment with trypsin, 3.8+/-1.2 after dispase, and 4.3+/-1.4 after immediate heating, or 2.2+/-0.7 cm/h after culture and heating. The dispase and heating methods disrupted the barrier to a greater extent than did the trypsin and culture-heating methods. The latter two methods allowed the kp to be maintained at low levels for 8 days (kp for trypsin 2.8+/-0.9 and 2.5+/-0.8 for culture-heating). Epidermis isolated by the trypsin or culture-heating techniques and maintained at the air-liquid interface can be used to study the mechanism by which barrier function is disrupted by chemicals.