EARLY ALTERATIONS OF ACTIN LN CULTURED HUMAN KERATINOCYTES AND FIBROBLASTS EXPOSED TO LONG-WAVELENGTH RADIATIONS - POSSIBLE INVOLVEMENT IN THE UVA-INDUCED PERTURBATIONS OF ENDOCYTOTIC PROCESSES

Exposure of cultured MRC5 human fibroblasts or NCTC 2544 human keratin ocytes to mild doses of ultraviolet A (UVA: 320-400 nm) radiations mar kedly decreased the actin reactivity with fluorescein-labeled phalloid in. This indicates a change in the degree of polymerization of actin a nd thus in the organization of actin filaments. Such a phenomenon migh t be involved in the previously reported UVA-induced inhibition of spe cific and nonspecific endocytotic processes.