IMAGING OF FLUORESCENT MOLECULE AND SMALL ION-TRANSPORT THROUGH HUMANSTRATUM-CORNEUM DURING HIGH-VOLTAGE PULSING - LOCALIZED TRANSPORT REGIONS ARE INVOLVED

During the application of high-voltage pulses across the skin, transpo rt of two negatively charged fluorescent molecules through the stratum corneum is highly localized. The apparent size of these localized tra nsport regions (LTR's) is initially 10 mu m in diameter for both calce in and sulforhodamine. Appearance of LTR's occurred at or above transd ermal voltages of 75 V. Ln the range of 75 to 160 V, the number of LTR 's increases with voltage, but their initial size is the same at all v oltages; with additional pulses LTR's increase in size, reaching diame ters of approximately 40-80 mu m. Small ion currents across the skin a re also localized and include the LTR's; however, the areas of current flux appeared to be larger. There was no visible damage to the struct ure of the skin seen at 100 x magnification for any of the voltages us ed (< 170 V across the skin). Significantly, LTR's are not sweat ducts or hair follicles.