Localisation of P2X(5) and P2X(7) receptors by immunohistochemistry in ratstratified squamous epithelia

In order to investigate whether purinoceptors are involved in the physiolog ical renewal and regeneration of epithelia, we used immunohistochemical tec hniques on fresh frozen sections of various stratified squamous epithelial tissues (cornea, tongue, soft palate, oesophagus, vagina and footpad) of th e rat and specific polyclonal antibodies to unique peptide sequences of P2X (1-7) receptors. Only two of the antibodies, anti-P2X(5) and anti-P2X(7), r eacted with epithelial structures. P2X(5) immunoreactivity was mainly assoc iated with the membranes of the proliferating and differentiating cell laye rs (spinous and granular layer) in both keratinised and non-keratinised epi thelia and growing hair follicles. In contrast, P2X(7) immunoreactivity was clearly associated with the keratinisation process, the staining being mos t intense in the upper keratinised and the exfoliated layers. These finding s suggest, for the first time, that P2X(5) and P2X(7) receptors play an imp ortant role in the physiological turnover of continuously regenerating cell s, and further, raise the possibility that they represent novel targets for the development of pharmacological tools of potential benefit for diseases of epithelial dysfunction.