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It has been found that nearly 50% of the lymph node and spleen macrophages (MP) of the CBA line mice contain DNA at levels superior to the diploid value (H2c--H4c in mononuclear MP, and up to H16c among polynuclear ones, the latter comprising 2.5-9.0% of the whole MP population). No DNA synthesis and mitosis were detected by autoradiography, cytophotometry, and cytomorphological analysis. During carcinogenesis the proportion of MP with elevated DNA amounts ("activated MPs") decreases due to their migration to tumours. Also immature MPs (1.6%) appear in the population, which synthesize DNA, but do not divide. Injection of retinoids restores the percentage of MPs with elevated DNA amounts to the levels characteristic of the intact animals, the fraction of DNA-synthetizing cells increasing up to 2.8%. It is proposed that retinoids may accelerate the processes of MP maturation, activation and renewing. A mechanism of cooperative action of MPs and retinoids is discussed in addition to the role of DNA hyper-replication. |
