[en] The effect of chlorpromazine (CPZ) and UVA on lysosomes of cultured normal human fibroblasts has been investigated. Acid phosphatase (ACPase) activity in 12000 g pellet of cells treated with CPZ (10 μg/ml) and UVA (6 x 10⁴ J/m²) was found to be decreased as compared with non-treated, CPZ or UVA treated control cells. This decrease, however, was not accompanied by a concomitant increase in ACPase activity in the 12000 g supernatant. The addition of Triton X-100 to cells pre-treated with CPZ + UVA resulted in only a moderate increase in ACPase activity of the 12000 g supernatant. ACPase activity of the cells incubated in media containing pre-irradiated CPZ was also found to be decreased. These results indicate that CPZ + UVA directly inactivate lysosomal enzymes, possibly without affecting the membrane. (author)