AbstractThe emergence of anionic sites during basement membrane zone formation was studied using migrating epidermis in organ culture as a model system. Ultrastructural investigations using a strongly cationized probe revealed that the anionic sites were found to be formed synchronously with the newly built basal lamina after 7 days in culture.Additionally, we examined the effect of chemically generated hydroxyl radicals on basal lamina‐associated anionic sites. Cytochemical studies showed that hydroxyl radicals produced a loss of cationic tracer positive anionic particles; this effect was inhibited by a specific scavenger, thiourea. These data might suggest that anionic sites were degraded by leukocyte‐derived hydroxyl radicals during acute inflammation near the dermal epidermal junction, resulting in disturbance of the charge‐selective permeability barrier.