It is difficult to differentiate the clinical features of actinic damage to the skin from that of chronological aging. Both processes are characterized by a proliferation of elastic fibers (elastosis) that results in the formation of elastotic material. There is some question as to whether this material is derived from pre-existing elastic fibers or represents an abnormal elastin-like substance. The aim of this proposal is to isolate and biochemically evaluate the elastotic material from hairless mouse dermits that has been irradiated with sunlamps. Elastin will be isolated using nondegradative techniques from irradiated and non-irradiated skin and compared as to its amino acid composition, extent of crosslinking, and quantitation of val-pro residues. In addition, the relative contributions of fibronectin, glycosaminoglycans, and microfibrillar proteins to the elastotic material in irradiated mouse dermis will be determined. The distribution of collagen and procollagen types in skin from irradiated mice will also be described. Techniques to be used include high pressure liquid chromatography to resolve and quantitate the amino acid, val-pro, and desmosine residues of elastin and enzyme linked immuno sorbant assay (ELISA) to quantitate microfibrillar proteins, fibronectin and collagen. In addition, immunofluorescent and immunoblotting methods will be employed. An in vitro model for the study of antinic effects on connective tissue will be developed. Human skin fibroblasts in vitro will be subjected to UV irradiation and its effects on collagen and elastin synthesis determined. In addition, variations in the levels of glycosaminoglycans, fibronectin, and microfibrillar proteins will be measured in these cultures. Biopsies will be obtained (from volunteers) from actinically damaged and non-exposed skin and the val-pro content, amino acid composition, and extent of crosslinking of the isolated elastin compared.