RESUMO
Sodium-copper chlorophyllin (SCC), a copper-porphyrin complex, has been shown to act as an inhibitor as well as a promoter of DNA-damage induction by a variety of mutagens in several test systems. In order to investigate the basis of this dual effect, experiments were carried out to compare the influence of pretreatment with intact SCC and that of its constituents, the metal-free protoporphyrin (PP-IX) and copper as CuCl(2). The wing-spot test was employed to monitor mutational events in somatic cells of Drosophila melanogaster. Heterozygous mwh+/+flr(3) larvae were treated for 24h with SCC, PP-IX, CuCl(2) or sucrose. Following this treatment, one group of larvae were immediately allowed to feed on instant medium containing 0.5mM N-nitroso-N-ethylurea (ENU) dissolved in phosphate buffer to reach pH 6. The remaining larvae received treatment with ENU with a delay of 1, 2 or 3days (DTD). Results revealed an (a) overall inhibitory effect for 0-DTD and 1-DTD after pretreatment with SCC, (b) only in 0-DTD after PP-IX, and (c) in all DTDs after treatment with CuCl(2). These results provide evidence that the copper ion plays a central role in the antimutagenic effect of SCC, and for a sustained period of time. Pretreatment with SCC and PP-IX produced a promoter effect at 2-DTD and 3-DTD. The results could be explained as an effect of the accumulation of metal-free porphyrin following the dissociation of the copper-porphyrin complex (SCC), the copper-ion reaching proteins to form complexes and participated in anabolic pathways.
Assuntos
Antimutagênicos/farmacologia , Clorofilídeos/toxicidade , Cobre/farmacologia , Etilnitrosoureia/toxicidade , Mutagênicos/farmacologia , Porfirinas/farmacologia , Animais , Clorofilídeos/química , Clorofilídeos/farmacologia , Drosophila/genética , Testes de Mutagenicidade , Relação Estrutura-AtividadeRESUMO
It was first demonstrated in Salmonella that higher and lower concentrations of chlorophyllin (CHLN) may have effects in opposite directions, higher doses inhibiting and lower doses promoting the mutagenic activity of certain tobacco-related nitrosamines. Previous work of our group demonstrated that CHLN may have both a promoter and an inhibitory effect on mutagenesis in Drosophila. The present paper reviews the evidence obtained in our laboratory using gamma rays as the mutagenic agent, that higher and lower pretreatment concentrations of CHLN are associated with inhibitory and promoting effects, respectively, as in Salmonella. Employing the wing spot test, 48h larvae were pretreated with various concentrations of CHLN from 0 to 69 mM and then treated with 10 Gy gamma rays. With the highest concentration of CHLN, an approximate 54% reduction in mutagenesis was observed. At 35 mM a remnant of this inhibitory effect was found in that a significant decrease was limited to the twin spot category. Evidence of promotion was first seen at 4.3mM CHLN, an effect which persisted for the remaining five lower concentrations, the most pronounced evidence of promotion being found at the four lowest concentrations, 0.03-1.1 mM CHLN. It should be noted that no evidence of genotoxicity was found for CHLN alone, an observation consistent with the several reports in the literature. The results are taken as strong evidence that pretreatment with low concentrations of CHLN promotes DNA damage induced by gamma rays in somatic cells of Drosophila.
Assuntos
Clorofilídeos/farmacologia , Clorofilídeos/toxicidade , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/efeitos da radiação , Raios gama/efeitos adversos , Mutagênicos/toxicidade , Animais , Clorofilídeos/administração & dosagem , Relação Dose-Resposta a Droga , Drosophila/genética , Testes de Mutagenicidade , Protetores contra Radiação/farmacologiaRESUMO
In Drosophila, 48h-old larvae were pretreated for 24h with chlorophyllin (CHLN) or sucrose and then treated with chromium(VI) oxide (CrO(3)) immediately following completion of the pretreatment period (0-day delay) or delayed 1, 2 or 3 days. The effects were scored in the wing spot test. After delays of 0 and 1 day, clear evidence of a protective effect of CHLN was found. Contrarily, after delays of 2 and 3 days, the results showed a reversal, i.e. CHLN-related events appeared more frequently than those in the sucrose control suggesting a promoting effect. It would appear prudent that CHLN be tested in a variety of situations in any given organism before decisions are reached regarding its inhibitor/promoter effects.
Assuntos
Antimutagênicos/farmacologia , Clorofilídeos/farmacologia , Compostos de Cromo/farmacologia , Drosophila/genética , Animais , Dano ao DNA/genética , Drosophila/efeitos dos fármacos , Drosophila/crescimento & desenvolvimento , Antagonismo de Drogas , Sinergismo Farmacológico , Feminino , Larva , Masculino , Sacarose/farmacologia , Asas de Animais/citologia , Asas de Animais/efeitos dos fármacos , Asas de Animais/crescimento & desenvolvimentoRESUMO
Evidence is presented that treating the Drosophila female with chlorophyllin (CHLN) has a marked effect on the yield of dominant lethals induced by the irradiation of sperm. The yield is significantly greater in the embryonic period (between the egg and the first instar) and is significantly reduced in postembryonic stages compared with a sucrose control.
Assuntos
Clorofilídeos/farmacologia , Drosophila/embriologia , Drosophila/genética , Protetores contra Radiação/farmacologia , Espermatozoides/efeitos da radiação , Animais , Drosophila/efeitos dos fármacos , Feminino , Larva/efeitos dos fármacos , Masculino , Sacarose/farmacologiaRESUMO
Irradiation of 96h old Drosophila following a 24h pretreatment with 5% chlorophyllin (CHLN) was delayed 0-4 days. The antimutagenic effect of CHLN in somatic cells monitored by the wing spot test persisted for 3 days after completion of the pretreatment and appeared to terminate at a time corresponding to the cessation of mitotic divisions of wing anlagen cells. Within the same population of cells, CHLN demonstrated both an inhibitory effect as measured in mwh single spot classes, and contrarily, a promoting effect in the class of mwh/flr twin spots and to an extent in the class of large flr spots. The reason for the contrasting effects of CHLN remains to be determined.
Assuntos
Antimutagênicos , Clorofilídeos/farmacologia , Drosophila/genética , Mutagênicos , Asas de Animais/efeitos da radiação , Animais , Clorofilídeos/toxicidade , Cruzamentos Genéticos , Drosophila/crescimento & desenvolvimento , Feminino , Larva/efeitos dos fármacos , Larva/efeitos da radiação , Masculino , Asas de Animais/efeitos dos fármacosRESUMO
The effect of chlorophyllin (CHLN) on the mutagenicity of four monofunctional alkylating agents (MFAAs) was evaluated in the wing spot test in Drosophila. Three of the compounds are direct-acting (ethylnitrosamine (ENU), methylnitrosourea (MNU), and methylmethanesulfonate (MMS)) and one indirect-acting (diethylnitrosamine, DEN). Results indicate that the mutagenicity of all four compounds is strongly inhibited by CHLN. The findings are not in agreement with the conclusion of Romert et al. (1992) that CHLN has no effect on the mutagenicity of direct acting MFFAs inferred from their work with MNU and ethylmethanesulfonate (EMS) in the V79 and Salmonella in vitro test systems. The results suggest the possibility that the action of CHLN need not include an inhibiting effect on metabolic activation.
Assuntos
Alquilantes/toxicidade , Antimutagênicos/farmacologia , Clorofilídeos/farmacologia , Drosophila/efeitos dos fármacos , Animais , Dietilnitrosamina/toxicidade , Relação Dose-Resposta a Droga , Drosophila/genética , Drosophila/metabolismo , Etilnitrosoureia/toxicidade , Feminino , Masculino , Metanossulfonato de Metila/toxicidade , Metilnitrosoureia/toxicidade , Mutagênese , Testes de Mutagenicidade , Asas de Animais/efeitos dos fármacosRESUMO
By delaying the time of gamma irradiation of 72 h larvae, pretreated at 48 h with 5% chlorophyllin (CHLN), it was established that the overall inhibiting effect of CHLN in somatic cells of Drosophila, as measured in the wing spot test, persists for about 4 days or until the time of cessation of the proliferation of wing anlagen. In the same population of cells, some spot classes gave evidence of an inhibitory effect whereas others did not arguing against the suggestion that the radioprotective effect of CHLN is a consequence of an induced delay in development, shrinking of the potential radiation target and lowering the probability of induced events. Other observations of interest are described.