POLY (ADENOSINE DIPHOSPHATE-RIBOSE) SYNTHESIS IN TRANSFORMED MOUSE EPIDERMAL CELLS IN CULTURE

Abstract

The activity of poly(adenosine diphosphate-ribose) (poly(ADP-ribose)) synthesis was examined in permeabilized transformed mouse epidermal cells (PAM 212 cells) in culture. PAM cells grown in low (0.02mM) Ca⁺⁺ medium showed a higher activity of poly(ADP-ribose) synthesis compared with the cells grown in normal (0.7mM) Ca⁺⁺ medium. Poly(ADP-ribose) synthesis was completely inhibited by 1mM 3-aminobenzamide, which is a specific inhibitor of poly(ADP-ribose) synthetase. PAM 212 cells grown in medium containing 2% fetal calf serum (FCS) switched from medium containing 15% FCS showed an increase of poly(ADP-ribose) synthesizing activity time-dependently during incubation. After PAM cells grown in normal Ca⁺⁺ medium were cultivated with 1α, 25-dihydroxyvitamin D₃ (1α, 25-(OH)₂-D₃) or TPA, poly(ADP-ribose) synthesizing activity decreased time-dependently, compared with the condition without addition, but an incubation with all-trans-retinoic acid (retinoic acid) did not show such an effect. Immunohistochemical analysis using anti-poly(ADP-ribose) antibody confirmed the increased poly(ADP-ribose) synthesis in nuclei of PAM cells grown in low Ca⁺⁺ medium. These results suggest that poly(ADP-ribose) synthesizing activity is correlated to proliferation and differentiation of epidermal cells.