Taurine levels and localisation in the stratified squamous epithelia

The content and distribution of the amino acid taurine in squamous epitheli a were studied using high-performance liquid chromatography and immunohisto chemical methods. Quantitative analysis demonstrated that taurine was highl y concentrated in the epidermis (5.49 mu mol/g fresh tissue in the hairless skin of the hind footpad of the rat), although the values in the isolated stratum corneum were extremely low (<0.073 <mu>mol/g in the horny layer of the same skin area). No other analysed amino acid (such as glutamate, gluta mine, glycine or alanine) showed this specific pattern of distribution. The immunohistochemical study revealed that in the dog and rat epidermis, taur ine was present in the keratinocytes of the granular and upper spinous laye rs. The basal layer, lower spinous layer and stratum corneum were immunoneg ative. A similar immunostaining pattern was found in the epithelia of the d ifferent organs studied: the mouth, tongue and oesophagus of the dog and ra t, the rat forestomach and the rat corneal epithelium. Other cell types, su ch as sebaceous and muscle cells, were immunolabelled. The existence of a c irculating pool of taurine in the epidermis (via taurine release from kerat inocytes before they reach the horny layer and its uptake by nearby cells) and its possible roles in these cells are discussed.