NITRIC-OXIDE INHIBITS DNA-SYNTHESIS AND INDUCES ACTIVATION OF POLY(ADP-RIBOSE) POLYMERASE IN CULTURED RAT HEPATOCYTES

Incubation of cultured rat hepatocytes with sodium nitroprusside or SI N-1, two nitric oxide (NO) donors, inhibited the mitogenic action of h epatocyte growth factor in a dose-dependent manner, The addition of 10 0 mu M reduced hemoglobin, which is known to absorb NO, or the presenc e of 20 mu M 1,5-isoquinolinediol, a poly(ADP-ribose) polymerase (PARP ) inhibitor, decreased the cytostatic effects of SIN-1, By labeling th e hepatocytes with [2-H-3]adenine we studied whether nitric oxide indu ces ADP-ribosylation of proteins in a whole-cell system. At 0.4 mM, so dium nitroprusside in. creased the [H-3]adenine labeling of two protei ns of 116 and 130-135 kDa, This effect was time-dependent and was dete cted after 2 h, Only the 116-kDa protein was recognized by three diffe rent antibodies against poly? (ADP-ribose) polymerase in Western blot assays, These results demonstrate that NO has antimitogenic effects in cultured hepatocytes and that its action could be mediated by PARP ac tivation. (C) 1996 Academic Press, Inc.