[Natural resistance of Drosophila melanogaster cells to 6-mercaptopurine and 8-azaguanine].

The growth of cells and the activity of some enzymes in diploid embryonic cells of Drosophila and Mosquito which cultivated for a long time in the presence of 6-mercaptopurine and 8-azaguanine were studied. It is shown on the culture of Drosophila cells that a high level of the resistance to 6-mercaptopurine and 8-azaguanine correlates with the absence of hypoxanthine-guanine phyosphorybosyltransferase (HGPRT) in them. HGPRT activity was not also revealed in extracts obtained from flies of different lines, which draws to the conclusion on the natural resistance of Drosophila cells to hypoxanthine and quanine analogues. Similar resistance was found out in Mosquito cell lines Mos 20 A. The second enzyme of such a type, adenine phosphoribosyltransferase, is present in the cells of all investigated lines. This fact explaines the retention of the sensitivity to adenine analogues in these cells.