The diminishing oocyte toxicity following intraperitoneal infusion of cisplatin (CDDP) combined with subcutaneous injection of sodium thiosulfate (STS) in syngeneic young mice

Small oocytes in 6-week-old C57BL/6 mice were destroyed in a dose-dependent fashion following intraperitoneal infusion of CDDP. ED65, the effective dose of which theoretically produced 65% destruction of small oocytes according to Probit analysis, was determined as 0.2mg/mouse. In this study, the oocyte toxicity induced with intraperitoneal treatment with CDDP (0.2mg) was offset by subcutaneous treatment with STS (40mg, 400 x molar ratio compared to that of CDDP). STS was subcutaneously injected into the back skin of mice at 60, 30, 15 minutes before, at the same time or at 15, 30, 60 minutes after the CDDP injection. STS markedly diminished the oocyte toxicity and reduced oocyte destruction about 45% when it was injected at 30, 15 minutes before or at the same time as CDDP infusion. On the other hand STS failed to reduce oocyte destruction when it was injected 15, 30 or 60 minutes later. STS might neutralize CDDP in the circulating blood to decrease the amount of active CDDP, but STS might not have any effect on CDDP once it is incorporated and conjugated with the DNA in the oocytes.