Influence of liposomal muramyl tripeptide phosphatidylethanolamine on the changes of nucleic acids in the blood and hemopoietic tissues of irradiated mice.

Effects of liposomal muramyl tripeptide phosphatidylethanolamine (MTP-PE/MLV) on nucleic acid content, and on DNA synthesis and cellularity in the blood and haemopoietic tissues of mice irradiated with a dose of 6 Gy gamma radiation were studied. It was found that injection of MTP-PE/MLV alone (200 micrograms per mouse; i.p.) resulted in a mild decrease in DNA content in the bone marrow as consequence of cellularity diminution in the femur. At the same time, incorporation of 3H-thymidine into bone marrow DNA increased in comparison to the non-stimulated mice. On the basis of simultaneous increase in RNA and DNA concentration in the blood we assume that the changes of nucleic acids and cellularity in the bone marrow of MTP-PE/MLV treated mice are related to the higher release of nuclear cells into the circulation. In mice irradiated 24 h after MTP-PE/MLV injection the decrease in nucleic acid content was similar to that in unprotected mice within the first three days after irradiation. However, during following days, the recovery of RNA and DNA content and cellularity in the bone marrow and blood proceeded at a much faster rate in mice protected by MTP-PE/MLV as compared to unprotected animals. The increase in DNA synthesis in the bone marrow of protected mice preceded the DNA content recovery. In the spleen and the thymus, no effect of liposomal MTP-PE was found.