Individual and strain differences in patterns of long-term persistence of urethane-induced sister chromatid exchanges (SCEs) in mouse lymphocytes and their relation to carcinogen susceptibility.
Using an improved microculture method, we investigated how the patterns of persistence of urethane-induced SCEs in lymphocytes differ among individuals and strains of mice (the ddY and C57BL strains), and we attempted to speculate on their relationship to carcinogen susceptibility. After a single intraperitoneal (i.p.) injection of 900 mg/kg of body weight of urethane into ten female mice each for the two strains, blood samples for the SCE analysis were collected from the tail vein at ten times during the 180 posttreatment days for each individual. Immediately after the treatment, SCE values increased to about three to four times the spontaneous values in all of the animals tested and then fell gradually. (The difference from spontaneous values was statistically significant until 120 days after the treatment.) Even after 180 days, however, some "outlier" cells with exceptionally high SCEs (greater than 20) persisted. Although there was some difference in average SCEs between the ddY and C57BL strains, the magnitude of the difference was too small to account for the difference between the strains in the incidence of urethane-induced malignancy. Also, when autopsy data at the 200th posttreatment day were matched individually with the data of SCE values within each strain, it was difficult to predict the individual risk of the occurrence of lung adenoma or other tumors from the relative difference in SCE values.
Endo
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Department of Hygiene and Preventive Medicine, Yamagata University School of Medicine, Japan.
Watanabe
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D000236:Adenoma / Q000139:chemically induced; D000818:Animals; D005260:Female; D008175:Lung Neoplasms / Q000139:chemically induced; D008214:Lymphocytes / Q000187:drug effects*; D008223:Lymphoma / Q000139:chemically induced; D051379:Mice; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000139:chemically induced*; D012854:Sister Chromatid Exchange / Q000187:drug effects*; D014520:Urethane / Q000633:toxicity*
D014520:Urethane