The micronucleus test with peripheral reticulocytes from phenacetin-treated mice.
The in vivo micronucleus test is conventionally performed using mouse bone marrow cells (BM assay). Using phenacetin as a test chemical, an alternative method using reticulocytes (RET assay) was examined to determine if this could be substituted for the BM assay. Single doses of 400, 600, and 800 mg/kg gave negative results 24 h after i.p. administration, but positive results were obtained with 600 and 800 mg/kg after 48 h. Responses were weak at 72 h. Double treatment enhanced the responses; 400 mg/kg gave a positive result. Maximum responses were generally reached 24 h after the second treatment, 48 h if doses were highly toxic. When the BM and RET assays were compared, the BM assay seemed to be slightly more sensitive than the RET assay; double treatment was superior to a single treatment in both BM and RET assays. Both assays can be used routinely but in the RET assay, sequential samples can be obtained from the same individuals without killing them, providing a firm basis to substitute it for the BM assay. Taking advantage of this characteristic of the RET assay, a regimen of double treatments and double sampling at 24 and 48 h is recommended for a wide range of doses. These data were obtained with CD-1 mice; MS/Ae mice gave a higher incidence of micronuclei than did the CD-1 strain.
Itoham Central Research Institute, Ibaraki, Japan.
N
N
Higashikuni
T
T
Baba
T
T
Nakamura
S
S
Sutou
D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D015162:Micronucleus Tests / Q000379:methods; D009153:Mutagens / Q000633:toxicity*; D010615:Phenacetin / Q000633:toxicity*; D012156:Reticulocytes / Q000187:drug effects*
D009153:Mutagens; D010615:Phenacetin