[Biological activity of transition metal complexes.  5.  Effect of dimethyl sulfoxide on the cytotoxic, antiviral and antitumoral properties of cis-dichlorodiammineplatinum (II): "cisplatin"]. 
In water or dimethyl sulfoxide solutions cis-platinum is subject of time depending solvolytic reactions leading to compounds with different biological effectivity.  Whereas the inactivation of vaccinia, vesicular stomatitis and adeno virus type 5 was not changed if dimethyl sulfoxide or dimethyl formamide instead of destilled water were used as solvents, long time stored solutions of cis-platinum in dimethyl sulfoxide were tolerated by cells cultivated in vitro in 8-25 times higher concentrations in comparison with a freshly solved preparation.  Their antiviral effectivity was maintained.  On the other hand experiments with mice showed that simultaneously with the decrease of toxicity of an aged cis-platinum solution in DMSO also its antileukemic activity disappeared.  In a 5 weeks old cis-platinum solution in destilled water antitumor activity was preserved in spite of enhanced toxicity.