RESUMEN
The effects of the route of benzo[a]pyrene administration on sister chromatid exchange (SCE) and B[a]P diol epoxide (B[a]PDE)-DNA adducts formation in bone marrow cells of Ah responsive (C57BL/6; B6) and Ah non-responsive (DBA/2; D2) mice were determined. Animals were treated intraperitoneally (i.p.), intragastrically (i.g.) or topically with two 100 mg/kg doses of benzo[a]pyrene 24 h apart and killed 96 h after the first treatment. Significant increase in the frequencies of SCE and the level of B[a]PDE-DNA adducts as measured by synchronous fluorescence spectrophotometry were detected in D2 mice as compared to B6 mice. The route of administration had little effect on SCE levels in bone marrow cells in D2 mice. In B6 mice higher levels of SCE were observed following i.p. administration as compared to i.g. or topical administration. In both strains the highest level of B[a]PDE-DNA adducts was formed after i.p. administration of B[a]P. We conclude that the i.p. route of B[a]P administration is the most effective in inducing SCE and B[a]P-DNA adducts formation. SCE induction does not correlate linearly with the amount of B[a]PDE-DNA adducts formed in these cells after administration of the above dose of B[a]P.
Asunto(s)
7,8-Dihidro-7,8-dihidroxibenzo(a)pireno 9,10-óxido/metabolismo , Benzo(a)pireno/administración & dosificación , Médula Ósea/metabolismo , Citocromo P-450 CYP1A1/biosíntesis , Aductos de ADN/metabolismo , ADN/metabolismo , Mutágenos/administración & dosificación , Intercambio de Cromátides Hermanas/efectos de los fármacos , Animales , Benzo(a)pireno/metabolismo , Médula Ósea/efectos de los fármacos , Citocromo P-450 CYP1A1/efectos de los fármacos , Vías de Administración de Medicamentos , Inducción Enzimática , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , Mutágenos/metabolismoRESUMEN
The effect of alleles of the Ah locus on the induction of sister-chromatid exchanges (SCE) was studied in C57Bl/6 and in DBA/2 mice treated twice intragastrically with benzo[a]pyrene (BP, 100 or 10 mg/kg b.w.). To measure the changes in the frequency of SCE, 2 protocols were used: in vivo in bone marrow cells after implantation of 5-bromodeoxyuridine (BrdU) tablets and in vivo/in vitro in spleen lymphocytes cultured with BrdU. On day 5 mice were killed and SCEs estimated in bone marrow cells. BP-DNA adducts in bone marrow and spleen were analyzed on day 5 after the same exposure to BP. In the spleen lymphocytes SCE frequencies were analyzed after an additional 48 h of culture. We found that at both doses of BP, the number of SCEs and BP-DNA adducts in bone marrow and in spleen cells was significantly higher in aryl hydrocarbon hydroxylase (AHH)-non-inducible (DBA/2) mice than in AHH-inducible (C57BL/6) mice. Only marginal induction of SCE was noted after the high dose of BP in C57BL/6 mice in bone marrow in vivo, whereas a highly significant increase in the frequency of SCEs was found in splenocytes in the in vivo/in vitro test. The spleen cells contained larger amounts of BP-DNA adducts and demonstrated higher absolute levels of SCEs than bone marrow cells. The sensitivity of both the in vivo/in vitro and the in vivo SCE test is high enough for assessment of Ah locus-linked differences in BP genotoxicity in mice at the prolonged time between treatment and cell preparation. The present data confirm the influence of inducibility of AHH in the intestine on the genotoxicity of BP to distal tissues after oral exposure to BP.
Asunto(s)
Benzo(a)pireno/toxicidad , Receptores de Droga/genética , Intercambio de Cromátides Hermanas/efectos de los fármacos , Animales , Médula Ósea/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Etilnitrosourea/efectos adversos , Linfocitos/efectos de los fármacos , Masculino , Metilcolantreno/toxicidad , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , Pruebas de Mutagenicidad/métodos , Receptores de Hidrocarburo de Aril , Bazo/efectos de los fármacosRESUMEN
The variant frequencies for 6-thioguanine-resistant spleen cells in different mouse strains have been estimated by autoradiography for animals without chemical treatment and in cases of in vivo mutagen dosage with ethylnitrosourea and cyclophosphamide, respectively. In untreated mice, the following variant frequencies have been found: C57Bl/6J, 2.84 x 10(-5);NMRI, 3.04 x 10(-5);DBA/2J, 5.91 x 10(-5). The selective concentration of 6-thioguanine was 100 microM for strains NMRI and DBA, while in the case of C57Bl with this concentration, no variant cells could be counted and a selective concentration of 50 microM was chosen. Treatment with 70, 140, and 210 mg/kg ethylnitrosourea resulted in increased variant frequencies in cells isolated 8 or 15 days later. On the other hand, doses of 20, 60, and 120 mg/kg cyclophosphamide did not result in a clear dose-response relationship of variant frequency in cells isolated 1, 8, 15, 22, and 29 days after treatment. These data are discussed with respect to findings in human populations exposed occupationally to cyclophosphamide.
Asunto(s)
Ciclofosfamida/toxicidad , Etilnitrosourea/toxicidad , Linfocitos/efectos de los fármacos , Bazo/efectos de los fármacos , Tioguanina/farmacología , Animales , Autorradiografía , Ciclofosfamida/administración & dosificación , Etilnitrosourea/administración & dosificación , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , MutaciónRESUMEN
In concanavalin A-treated cultures TCDD (10(-8)M) inhibited proliferation of mouse spleen lymphocytes in cells of C57B1/10/mice by 65% and in cells of DBA/2 mice--by 42%. In phytohaemagglutinin-treated cultures of spleen lymphocytes of both strains TCDD produced no significant decrease in incorporation of 3H-thymidine into DNA. These observations indicate that effects of TCDD on lymphocyte proliferation are mediated by pleiotropic activity of Ah gene.