title: Circadian variation in the susceptibility of mouse epidermis to chemical carcinogens.
abstract: Groups of hairless nice were given a single topical application of each of two highly-reactive carcinogens (methylnitrosourea and beta-propiolactone) at 12(00) and 00(00). The tumor yield was as follows: for methylnitrosourea there was a slightly higher yield of skin tumours in the animals painted at 12(00); for animals painted with beta-propiolactone, there was a significantly higher skin tumour yield in those painted at 12(00). When the groups painted with the two carcinogens are considered together, there was a significantly higher number of animals with all types of tumours in the group painted at 12(00). Hence, there seems to be a circadian variation in the sensitivity of a tissue to a single contact with a chemical carcinogen. This may be related to the proliferative state of the tissue involved: at 12(00), DNA and cell division takes place at a more rapid rate than at 00(00).
mesh_terms: D000236:Adenoma / Q000139:chemically induced; D000818:Animals; D002940:Circadian Rhythm; D004347:Drug Interactions; D008175:Lung Neoplasms / Q000139:chemically induced; D008770:Methylnitrosourea / Q000008:administration & dosage; D051379:Mice; D008812:Mice, Hairless; D010212:Papilloma / Q000139:chemically induced; D011420:Propiolactone / Q000008:administration & dosage; D012878:Skin Neoplasms / Q000139:chemically induced*; D013997:Time Factors
chemical_list: D008770:Methylnitrosourea; D011420:Propiolactone