Effects of different mitogens on intrasplenic liver tissue transplants in comparison to orthotopic liver

Ectopic liver cell transplants, when compared to orthotopic liver, can serve as a tool to study topic influences on liver cell differentiation, multiplication, function and responsiveness to xenobiotics. The aim of the present study was to evaluate, if characteristic effects of mitogens are exerted in both liver and intrasplenic liver cell transplants in a similar manner. Fetal liver tissue suspensions were transplanted into the spleens of adult male syngenic rats. Four months later, transplant recipients and controls were treated with fluorene (FEN), fluorenone (FON), 2-acetylaminofluorene (AAF), N-nitrosodibenzylamine (NDBA) or the solvent 48 hours before sacrifice. The following parameters were assessed within livers and spleens: mitotic activity of hepatocytes, glycogen content, cytochrome P450 (P450) isoforms expression, P450 mediated monooxygenase functions, tissue content of lipid peroxides (LPO) and of reduced and oxidized glutathione (GSH; GSSG). In both orthotopic livers and intrasplenic transplants FEN, FON or NDBA administration increased the mitotic activity of the hepatocytes. Treatment with the mitogens caused a distinct and characteristic induction of the P450 isoforms expression and of the respective monooxygenase functions in the livers and (with certain differences) also in the transplants. FEN and FON slightly increased, AAF and NDBA reduced liver glycogen content. The latter effect was also seen in the transplants. NDBA administration caused a slight increase in tissue LPO content in livers, but not in spleens. Additionally, AAF or NDBA treatment led to an elevation of liver (but not of spleen) GSH and GSSG concentrations. The results of the present investigation show that characteristic effects of mitogens on orthotopic liver occur with certain differences also in ectopic liver cell transplants.