A protein reminiscent of the epidermal SH-protease inhibitor occurs in squamous epithelia of man and rat.

The occurence of the human and rat epidermal SH-protease inhibitors in various human and rat tissues was studied by double radial immunodiffusion against specific antisera to the inhibitors. An immunoreactive protein was found in the extracts prepared from human and rat epidermis and from eosophageal and vaginal squamous epithelia, and from rat pro-ventricular squamous epithelium. No immunoreactive protein was found in man or rat in any other of their tissues, studied by us. The results strongly suggest that a protein reminiscent of the human or rat epidermal SH-protease inhibitor is present in squamous epithelia but not in other tissues. The identity of the epidermal inhibitor and the immunoreactive protein in the other squamous epithelia was confirmed by immunodiffusion, immunoelectrophoresis and gel chromatography, and by immunoinhibition of the papain inhibiting activity of the human epidermal and oesophageal inhibitors by gammaglobulins separated from antiserum to the human epidermal inhibitor.