Site-specific protein synthesis in liver regeneration determined by PET

Site-specific regeneration of the liver after 70% partial hepatectomy was investigated noninvasively in terms of protein synthesis using PET with L-[methyl-11C]methionine in a living animal. Protein synthesis in rat liver at 24 hr after partial hepatectomy did not occur uniformly in the whole liver but intensely in the middle part of the regenerating organ in comparison with the other parts. The activity was significantly low at the posterior aspect of the liver. On the other hand, site-specific protein synthesis was not observed in normal liver. These results were confirmed by bioimaging analyzer system (BAS) analysis, an invasive method that indicates radioactivities of precise intrahepatic sites. DNA synthesis in regenerating liver was also monitored with [2-14C]thymidine and analyzed by BAS 24 hr after 70% hepatectomy. Site-specific DNA synthesis in regenerating liver corresponding to the protein synthesis was also observed by BAS analysis. These results indicate that liver regeneration occurs intensely in the middle part of the liver and that PET enables noninvasive in vivo biochemical analysis.