Effect of intraperitoneal administration of lentinan on rats with carcinomatous peritonitis

The aim of this study is to assess the effect of intraperitineal administration of lentinan on rats with malignant ascites and to investigate the immunological machanism which leads to the prolongation of survival time. Donryu rats (6 weeks of age, famale) bearing AH13, AH130, AH66, AH66F carcinomatiosis received intraperitoneal injection of lentinan (1mg/kg) or saline alone beginning one day agter tumor challenge. Survival was significantly prolonged in rats bearing AH13 by administration of lentinan (P＜0.05). Therefore rats bearing AH13 were used in this study. The schedule of lentinan or saline administration was same as above. Immunological parameters such as subsets(OX^19＋, W3/25^＋, OX8^＋) of blood lymphocytes(BL) and peritoneal exudate lymphocytes (PEL), and cytotoxic activities of blood mononuclear cells (BMC) were measured in lentinan group (L group), saline group no difference in each group, whereas in L group, the percentage of suppresor/cytotoxic T cells of PEL was increased. Anti-AH13 activities of BMG were lower as compared with NB and C group. These results indicate that cytotoic T cells play an important role on tumor regression in the perotoneal cavity. Intraperitoneal administration of Lentinan may by a new effective immunotherapy for carcinomatous peritonitis in humans.