TPA AND CYCLOHEXIMIDE MODULATE THE ACTIVATION OF NF-KAPPA-B AND THE INDUCTION AND STABILITY OF NITRIC-OXIDE SYNTHASE TRANSCRIPT IN PRIMARY NEONATAL RAT HEPATOCYTES

12-O-Tetradecanoylphorbol 13-acetate (TPA) elicited a transient increa se in the transcription of the inducible nitric oxide synthase (iNOS) gene coupled with a shortening of the half-life of its mRNA in primary neonatal rat hepatocytes. These effects of TPA were preceded by a sur ge in nuclear translocation of the transcription factor NF-kappa B, an d followed by a mounting accumulation of NO2- in the growth medium. Ev en cycloheximide (CHX) added by itself elicited an early, sustained ac tivation of NF-kappa B followed by an intense induction of iNOS gene e xpression, irrespective of what degree of protein synthesis inhibition was brought about by the several concentrations tested, When given to gether, TPA and CHX exerted additive effects on hepatocellular iNOS mR NA levels. These results suggest the likelihood of an ordered sequence of events by which an activated NP-kappa B mediates the induction of iNOS gene expression in TPA-and/or CHX-treated primary hepatocytes.