The proposed research involves the use of primary neonatal mouse and adult human keratinocytes in culture to define the modulation by agents of epidermal cell function. Function is defined for the purposes of this study as proliferation as assayed by 3H-TdR incorporation into isolated DNA and autoradiographic determination of the labeling index, and differentiation defined as the production and final assembly of structural proteins (keratins, keratohyalin, filaments, cornified cell envelopes) by the keratinocytes. Differentiation is quantitatively and qualitatively measured by 3H histidine pulse labeling of the cultures and determination of 3H uptake into sequentially extracted fractions: the high molarity salt extractable proteins (soluble keratohyalin and keratohyalin macroaggregates); SDS soluble proteins (viable cell contents); 4M urea soluble proteins (fibrous proteins); and 8 M urea plus reducing agent soluble and insoluble fractions (disulfide cross-linked keratins and cornified envelope, respectively). SDS polyacrylamide gel electrophoresis is used to further isolate and classify the labeled proteins. A possible precursor-product relationship between epidermal cell differentiation proteins as been suggested by our studies to date. We propose to study the changes in 3H-histidine labeled proteins as the cultures grow over time and to determine the effect of protein synthesis inhibitors, i.e., puromycin, on shifts of labeled proteins between the different categories. We propose to investigate the proliferative response of adult human epidermal cells in culture and neonatal mouse in cultures to glucocorticoids, cyclic nucleotides, retinoid derivatives and epidermal hyperlastic agents, alone and in combination. The results of the proposed investigations can yield information contributing to an understanding of epidermal cell control mechanisms and can result in improved therapies for the treatment of cell proliferation-differentiation disorders, specifically, psoriasis.