Thermosensitizing Effects of Amiloride and 4,4-Diisothiocyanatostilbene-2,2'-disulfonic Acid on FsaII Mouse Fibrosarcoma

Enhancement of the hyperthermia effect in FsaII fibrosarcoma of C3H mice in vivo by amiloride and 4,4- diisothiocyanatostilbene.2,2'-disulfonic acid (DIDS) was studied. Heating alone significantly increased the tumor lactic acid content and lowered the tumor energy levels, as indicated by the PCr and ATP contents which were measured using invasive chemical analysis. An i.p. injection of amiloride, DIDS, or amiloride combined with DIDS prior to heating further increased the lactic acid content and reduced the energy status in the tumors. Amiloride and DIDS may be useful in increasing the therapeutic efficacy of hyperthermia treatments by enhancing the reduction in tumor pH.