Activation of poly(ADP-ribose) polymerase-1 (PARP-1) in response to DNA damage is an important mechanism to keep homeostasis or to trigger apoptosis. The expression and function of (PARP-1) was studied in primary cells cultured from human lung. Normal human bronchial epithelial cells (NHBEC) and peripheral lung cells (PLC) from lung cancer patients were grown as explant cultures and were followed over a period of 12 weeks. PARP-1 protein was expressed in all explant cultures from bronchial epithelium. The levels of PARP protein differed between individuals by a factor of 2.3 in the first explant. Three cases were followed for more than 100 days. The expression levels varied intra-individually by a factor of 1.3-1.4 over this time period. PARP-1 activity was determined immunohistochemically after induction of DNA damage with H(2)O(2) (0.05-0.3 mM, 5 min). The fluorescence signal for ADP-ribose polymers attached to chromatin proteins correlated well with the concentration of H(2)O(2). PARP-1 activity differed by a factor of 3.1 in NHBECs obtained from the first generation of explants from 11 cases. PARP-1 activity is present in NHBECs until the 8th and in PLCs until the 12th week and declined to about half of the start level. Primary cultures of NHBECs and PLC are suitable to study the effect of external factors on PARP-1 expression and function.