Effects of intraperitoneal administration of potassium 2,5-dihydroxyphenyl sulfonate (DHPS) and potassium 2,5-diacetoxyphenyl sulfonate (DAPS) on the progression of tumors established in rats by subcutaneous implantation of rat glioma C6 cells (5 × 10
cells). Photographs show tumors removed from rats treated with vehicle (0.9% NaCl; n = 11; A), DHPS (100 mg/kg/d; eq. to 0.44 mmol/kg/d, i.p. for 10 days; n = 12; B), or DAPS (100 mg/kg/d, eq. to 0.32 mmol/kg/d, i.p. for 10 days; n = 13; C). Treatment began once the presence of a tumor was verified on the fifth day after glioma cell implantation. Tumors were removed after 10 days of treatment and the empty spaces in panel C correspond to tumors that had completely regressed after DAPS treatment (N.D., not detected). A 10 mm bar is displayed in each image. Panels D and E show the quantification and comparison of the volumes and weights, respectively, of the tumors developed in rats treated with vehicle (VEH), DHPS or DAPS. The data are expressed as the mean ± SEM. numbers of animals are shown in parenthesis. *p < 0.05; **p < 0.01; ***p < 0.001 vs. VEH; † p < 0.05 vs. DHPS, by one-factor ANOVA followed by Student-Newman-Keuls test. Panel F shows the effects of subcutaneous glioma development and the treatment with DHBS and DAPS on serum concentrations of lactate dehydrogenase (LDH) in rats. The data are expressed as the mean ± SEM of the percentage of serum LDH detected in control, not bearing glioma, rats (CON). Numbers of animals are shown in parenthesis. *p < 0.05; **p < 0.01; vs. CON; † p < 0.05 vs. VEH, by one-factor ANOVA followed by Student-Newman-Keuls test.