Ž . Mutation Research 389 1997 157–165 Sodium azide induces mitotic recombination in Drosophila melanogaster larvae Edna Gonzalez-Cesar, Patricia Ramos-Morales ) ´ ´ Laboratorio de Genetica, Facultad de Ciencias, UniÕersidad Nacional Autonoma de Mexico, Coyoacan, 04510 Mexico D.F., Mexico ´ ´ ´ ´ ´ Received 26 April 1996; revised 16 September 1996; accepted 1 October 1996 Abstract Ž . Sodium azide NaN , a potent mutagen for bacteria and barley, was tested for somatic mutation and mitotic 3 recombination induction in wing imaginal disc cells of Drosophila melanogaster. Comparisons were made among 3 () 3 inversion-free flr r mwh, inversion-heterozygous TM3, Ser r mwh, and inversion-free, high bioactivation OR R , flr r mwh flies. Third instar larvae were exposed chronically for 48 h to sodium azide at 0.5, 0.63. 0.75, 0.88 and 1.0 mM. The frequencies of spots per wing obtained in the three kinds of progeny scored were compared. In inversion-free flies, sodium azide induced large single and total spots at all concentrations tested, and small single and twin spots at 0.75 mM and higher concentrations. In contrast, it failed to increase the frequency of small and large single spots in inversion-heterozygous flies. Ž . In high bioactivation flies which are inversion-free , sodium azide increased the frequency of large single spots at 0.63, 0.88 and 1.0 mM and the frequency of total spots at 0.63 mM. From the absence of genotoxic activity observed in inversion-heterozygous flies it is concluded that sodium azide induces exclusively mitotic recombination in wing somatic cells of Drosophila melanogaster larvae after chronic exposure. This recombinogenic activity is reduced in the presence of high bioactivation capacity. Ž . Keywords: Mitotic recombination; Somatic mutation and recombination test SMART ; Sodium azide; Drosophila melanogaster ; Genotoxicity; Metabolic activation Ž . Sodium azide NaN is a common laboratory 3 chemical, and a widely used compound in industry, agriculture, medical practice, and organic synthesis research. In addition, this chemical has been used as wx a nitrogen gas generator in airbags for cars 1 . The mutagenic potential of sodium azide has been re- ported for several screening assays. Sodium azide ) Ž .Ž . Ž .Ž . Corresponding author. Tel.: 52 5 622-4906; Fax: 52 5 622-4828; E-mail: prm@hp.fciencias.unam.mx Ž . reverts strain TA1530 a base-substitution mutant of S. typhimurium but is ineffective in strains TA1531, Ž . wx TA1532 and TA1534 frameshift mutants 2 . Data obtained from barley seeds germinated in the pres- ence of azide confirm that this compound may act as wx a point mutagen during DNA replication 3 . How- wx ever, Ciesla and Filutowicz 4 found that the inhibi- tion of DNA replication before azide treatment did not modify the mutagenic response, and hence, DNA replication during treatments with azide is not neces- sary for its mutagenic action. wx Owais et al. 5 found experimental evidence for 1383-5718r97r$17.00 Copyright q 1997 Elsevier Science B.V. All rights reserved. Ž . PII S1383-5718 96 00142-5