Modulation of the antitumor effect and tissue distribution of highly branched (1-->3)-beta-D-glucan, SSG, by carrageenan.

The action of carrageenan (CAR), a representative blocking reagent for phagocytes, on the antitumor effect and tissue distribution of highly branched (1-->3-beta-D-glucan, SSG, was examined. CAR inhibited the antitumor effect of intraperitoneally administered SSG only when applied before inoculation of the tumor, and had little effect when applied after tumor inoculation. A similar result was observed when SSG was administered intralesionally. In contrast, CAR had considerable effect on tissue distribution of i.p. SSG. The differences with respect to the results in normal mice were: 1) the distribution of SSG from the peritoneal cavity to the rest of the body was inhibited, 2) large numbers of peritoneal exudate cells (PEC) were produced and a relatively high concentration of 3H-SSG was found in the PEC fraction 48h after administration of 3H-SSG, 3) one week after administration, 3H-SSG was distributed to throughout the body but the amount of 3H-SSG distributed was lower than in normal mice, 4) a significant amount of 3H-SSG was recovered from ligaments (containing omental milky spots, peritoneum, mesentery and associated fat) in which negligible amounts were found in normal mice. The results suggest that the inhibition of the antitumor effect of SSG by CAR probably results from the prevention of the natural resistance of mice which is related to phagocytic function, and that the distribution of SSG to throughout the body is significantly modulated by CAR.