Ultrastructural localization of cAMP-dependent protein kinase subunits in regenerating rat hepatocytes using immunogold electron microscopy.

We have used the indirect colloidal immunogold technique to examine the ultrastructural localization and distribution of the regulatory subunits (RI and RII) and catalytic subunit (C) of cAMP-dependent protein kinase (cA-PK) in hepatocyte nuclei during the prereplicative phase of rat liver regeneration. The technique allowed the localization of all three subunits of cA-PK in hepatocyte nuclei. Morphometric quantitation of the relative staining intensity of nuclear antigen indicated a marked increase of immunogold staining of nuclear RI and C 16 hours following partial hepatectomy. In contrast, staining of nuclear RII was not affected. These immunocytochemical observations correlate well with our previous data (Laks, M.S. et al. (1981) J. Biol. Chem. 256, 8775-8785) obtained by biochemical methods indicating a modulation of cA-PK activity after partial hepatectomy.