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 SIN-1, two nitric oxide (NO) donors, inhibited the mitogenic action of hepatocyte growth factor in a dose-dependent manner. The addition of 100 microM reduced hemoglobin, which is known to absorb NO, or the presence of 20 microM 1,5-isoquinolinediol, a poly(ADP-ribose) polymerase (PARP) inhibitor, decreased the cytostatic effects of SIN-1. By labeling the hepatocytes with [2-3H]adenine we studied whether nitric oxide induces ADP-ribosylation of proteins in a whole-cell system. At 0.4 mM, sodium nitroprusside increased the [3H]adenine labeling of two proteins of 116 and 130-135 kDa. This effect was time-dependent and was detected after 2 h. Only the 116-kDa protein was recognized by three different 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 activation.