Influence of L-asparaginase on spleen colony formation in mice.

L-asparaginase pretreatment prior to sublethal whole body irradiation resulted in decrease of endogenous spleen colonies. This effect was abolished by the simultaneous addition of L-asparagine. L-asparaginase administered after sublethal irradiation did not reduce the number of spleen colonies. This result agrees with the suggestion that L-asparaginase inhibits the proliferation of undifferentiated but not of differentiated cells.