Influence of reticuloendothelial function on the growth of transplantable rat ascites hepatoma (AH-130).

Abstract

Experimental studies were performed to clarify the non-specific defense mechanism of the host (Donryu rat) against tumor growth, chiefly from the view-point of the function of the reticuloendothelial system (RES). The functional activity of the RES, as determined by carbon clearance and the percentage of subcutaneous prehistiocytes, and the grade of the growth of rat ascites hepatoma cells (AH-130) were studied following the intraperitoneal administration of various agents such as polyvinyl pyrolidone (PVP), Evans blue and zymosan. In rats treated with PVP or Evans blue, the RES-function was inhibited and tumor growth was not influenced, whereas in rats administered with zymosan the RES-function was stimulated and tumor growth was inhibited. Thus, intraperitoneally admin-istered zymosan was proved to be effective in tumor inhibition; however, it was also ascertained that zymosan itself did not influence tumor growth in vitro. In addition, almost similar tumor inhibition to that in zymosan treated rats was observed with the recipient rats, which received peritoneal reactive cells obtained from the ascites of zymosan treated donor rats. Such tumor inhibition, induced by transferred peritoneal reactive cells, was most pronounced in cases which had received these cells prior to tumor inocula-tion. In addition, this tumor inhibitory effect became more prominent from about the 7th day of tumor inoculation. It seems adequate to assume from these results that the resistance of the host pretreated with zymosan against tumor growth can be sustained by ‘reactivity of the peritoneal cavity’ to zymosan or a ‘non-specific defense mechanism’ linked to the hyperactivity of the RES induced by zymosan.