Taenia taeniaeformis: inhibition of metacestode development in the rat by gossypol.

The effect of gossypol, a polyphenolic compound, on developing Taenia taeniaeformis larvae in the rat liver was examined. Five groups of rats were used. In group 1, subcutaneous injection of gossypol at 10 mg/kg was started 5 days prior to administration of tapeworm eggs. In group 2, gossypol injections were started 5 days after administration of eggs. Groups 3 and 4 were infected and noninfected rats, respectively, which received the vehicle (10% ethyl alcohol in 0.85% NaCl) only. Group 5 rats were noninfected but received gossypol. From each group, 5 rats were killed on days 7, 12, and 22 of infection, respectively. The number and size of larvae and the size of the livers were much less in rats gossypol injected 5 days before infection than those in the vehicle-treated group. Administration of gossypol 5 days after infection resulted in less inhibition. The size and the thickness of the fibrous capsule around larvae of the gossypol-treated rats were much smaller than those of the control-infected group. The actively developing larvae excrete or secrete a sulfated glycosaminoglycan which is specifically stained with alcian blue. There was much more alcian blue-positive substance around the larvae and the capsule of the control-infected liver compared to the gossypol-treated infected animal. The percentage body weight of the spleen was significantly greater in the gossypol-treated rats in both infected and noninfected groups. These results suggest that gossypol may directly inhibit tapeworm larval development or that elimination of the tapeworm may be resulted from gossypol-induced stimulation of host cell-mediated immunity.