Article révisé par les pairs
Résumé : Normal mouse peritoneal macrophages produce in vitro soluble factors inhibiting tritiated thymidine (3HTdR) incorporation by melanoma cells. The inhibitory effect of 106 macrophages/ml was equivalent to 10-3 mg/ml of thymidine. Large amounts of thymidine were detected by thin layer chromatography in normal macrophage culture supernatants. In contrast, transformed macrophage cell line supernates were found to be devoid of detectable thymidine. This phenomenon was shown to be due to the lack of thymidine kinase in normal macrophages and to its recovery in transformed macrophages. Processing of radiolabelled precursors of TdR into labelled TdR, such as 6-14C-orotic acid and 3H-TMP was demonstrated by ascending paper chromatography. Since thymidine is a potent cytostatic, its production by macrophages could be a mechanism of non specific modulation of tumour cell growth within the cellular microenvironment of the macrophage.