title: Role of O6-alkylguanine-DNA alkyltransferase in the resistance of mouse spermatogenic cells to O6-alkylating agents.
abstract: The O(6)-alkylguanine-DNA alkyltransferase inactivator O(6)-benzylguanine was administered to BALB/c mice either alone or before exposure to 1,3-bis(2-chloroethyl)-1-nitrosourea to study the role of the DNA repair protein O(6)-alkylguanine-DNA alkyltransferase in the protection of the testis against anti-cancer O(6)-alkylating agents. Exposure of the mice to 1, 3-bis(2-chloroethyl)-1-nitrosourea or O(6)-benzylguanine alone did not produce any marked testicular toxicity at the times studied. Testicular O(6)-alkylguanine-DNA alkyltransferase concentrations were assayed between 0 and 240 min after O(6)-benzylguanine treatment and were shown to be > 95% depleted 15 min after treatment with O(6)-benzylguanine and remained at > 95% at all the times assayed. Histological examination, the reduction in testicular mass and the induction of spermatogenic cell apoptosis showed that this depletion significantly potentiated 1, 3-bis(2-chloroethyl)-1-nitrosourea-induced testicular damage after treatment. Major histological damage was apparent 42 days after treatment, demonstrating that the stem spermatogonia were significantly affected by the combination. These results demonstrate that O(6)-alkylguanine-DNA alkyltransferase plays a significant role in protecting the spermatogenic cells from damage caused by DNA alkylation and indicate that the observed toxicity may result from damage to stem spermatogonia.
authors.affiliation: Clinical Oncology Unit, University of Bradford, Bradford BD7 1DP, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Thompson
authors.forename: S
authors.initials: S
authors.lastname: Abdul-Rahman
authors.forename: T G
authors.initials: TG
authors.lastname: Baker
authors.forename: J A
authors.initials: JA
authors.lastname: Rafferty
authors.forename: G P
authors.initials: GP
authors.lastname: Margison
authors.forename: M C
authors.initials: MC
authors.lastname: Bibby
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000493:pharmacokinetics / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D002330:Carmustine / Q000493:pharmacokinetics / Q000633:toxicity*; D004260:DNA Repair / Q000187:drug effects; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006207:Half-Life; D020287:In Situ Nick-End Labeling; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000037:antagonists & inhibitors* / Q000502:physiology*; D012670:Seminiferous Epithelium / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D013093:Spermatogonia / Q000187:drug effects* / Q000473:pathology; D013737:Testis / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D013997:Time Factors
chemical_list: D018906:Antineoplastic Agents, Alkylating; D004791:Enzyme Inhibitors; C064976:O(6)-benzylguanine; D006147:Guanine; D019853:O(6)-Methylguanine-DNA Methyltransferase; D002330:Carmustine