Tissue specificity of the epidermal chalones.

An increasing body of evidence indicates that the rate of cell renewal in labile and stable cell populations is regulated according to a negative feedback principle. Water extracts of such tissues contain mitosis-inhibiting substances (chalones) that probably represent the chemical signals in these cell populations. Tissue specificity is one of the theoretical prereguisites of the chalones but has not been proven in many cases. The present study is an attempt to evaluate the tissue specificity of some chalones, with special emphasis on the chalones found in keratinizing epithelium of the forestomach, and the epithelium of the crypts of jejunum and colon were chosen since they represent stady state systems with a well defined proliferating ppol...