Circadian variation in the induction of intestinal tumors by N-methyl-N-nitrosourea in male C57BL/6N mice.
Male C57BL/6N mice were administered a single ip injection of 30 mg of N-methyl-N-nitrosourea (MNU)/kg of body weight. Additional groups were treated similarly every 3 hours for the next 24 hours. Adenocarcinomas of the small intestine were the major treatment-related tumors, with the total incidence being 38% at 250 days after injection. There was a significant circadian variation for tumor induction; the maximum number of intestinal tumors (approximately equal to 55%) tended to occur when the MNU was administered during the middle of the light period (6:00 to 18:00), while the tumor incidence was at a minimum (approximately equal to 10%) when the MNU was given in the middle of the dark phase (18:00 to 6:00). These data are discussed in relation to DNA synthesis and repair and MNU-induced cellular toxicity.
Beland
F A
FA
National Center for Toxicological Research (NCTR), Jefferson, AR 72079.
Dooley
K L
KL
Sheldon
W G
WG
Delongchamp
R R
RR
D000230:Adenocarcinoma / Q000139:chemically induced; D000818:Animals; D002940:Circadian Rhythm; D004247:DNA / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D007414:Intestinal Neoplasms / Q000139:chemically induced*; D007421:Intestine, Small; D008297:Male; D008770:Methylnitrosourea / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL
D008770:Methylnitrosourea; D004247:DNA; C015558:O(6)-methyl-2'-deoxyguanosine; D003849:Deoxyguanosine