Further studies of the effect of pepstatin on ascites accumulation in tumor-bearing mice.

Studies were done of the effect of pepstatin on ascites accumulation in mice bearing MM46, Ehrlich, CCM, SN36, L1210, and NTF ascites tumors. When pepstatin was injected subcutaneously at 80 mg/kg body wt before ascites accumulation, it inhibited the accumulation in all strains of the tumors tested. In MM46, CCM and NTF tumor strains there was also a decrease in the tumor cell numbers following pepstatin treatment. Kinetic studies on ascites accumulation with tumor strain MM46 demonstrated that even when pepstatin was injected after ascites accumulation it reduced the ascites volume. A dose-dependent effect was observed in this tumor strain when pepstatin was injected both before and after ascites accumulation. The results confirm previous studies of pepstatin's ability to retard ascites in L1210 and P-815Y ascites tumors and also broaden the concept of the mechanisms by which petstatin may be acting.