Elemental changes in guinea-pig epidermis in the hyperplastic response to irritant stimuli

A mild irritant reaction was induced by application of sodium lauryl sulphate to the skin of guinea-pigs. The response was analysed at 24 and 48 h after application using light microscopy, transmission electron microscopy and energy dispersive X-ray microanalysis (EDX). It was found that the sodium lauryl sulphate induced a hyperplastic response in the epidermis with an increased number of keratinocytes. This response was associated with significantly increased levels of intracellular sodium and chloride. The elemental changes were most marked at 24 h, whereas the number of keratinocytes was highest at 48 h. The pattern of the elemental changes and the ultrastructural alterations are compatible with initial membrane damage followed by a transient increase in proliferative activity. The present results demonstrate that EDX is a useful tool for the analysis of functional alterations in epidermal keratinocytes under pathological conditions.