NUCLEAR-LOCALIZATION OF PARATHYMOSIN IN RAT AND HUMAN HEPATOCYTES - ALIGHT AND ULTRASTRUCTURAL-STUDY

Parathymosin (ParaT) is an almost ubiquitious peptide first isolated f rom rat thymus, the highest concentration being in the liver. Its subc ellular localization is controversial and both a cytoplasmic and a nuc lear distribution have been reported. The aim of the present work was to study the intracellular localization of ParaT in rat and human live rs by light immunohistochemistry and immunoelectron microscopy procedu res. Both in rat and human livers immunostaining for ParaT was found i n the nuclei of hepatocytes, the nucleoli and the cytoplasms being neg ative. The intensity of immunostaining was variable from cell to cell, but virtually all hepatocytes were positive. No immunoreactivity was found in non-parenchymal cells. Immunogold labelling confirmed these r esults and showed that ParaT immunoreactivity was associated with both euchromatin and heterochromatin. Our results demonstrate that ParaT i s localized in the nucleus of hepatocytes and support the idea that th e inactivation of the cytoplasmic enzyme phosphofructokinase-1 is not the unique function of ParaT.