title: Enhancement of tumor growth under short light/dark cycle in mouse lung.
abstract: We examined whether a change in daily light/dark cycle affected DNA synthesis and tumor growth in mouse lung. Both CD-1 and A/J mice, which were treated with urethane and maintained under the short light/dark cycle (6 h light, 6 h dark), developed significantly larger sizes of lung tumors than the mice maintained under the standard light/dark cycle (12 h light, 12 h dark), indicating that short and frequent light/dark cycles enhanced tumor growth. When 3H-labeled thymidine was injected and incorporated radioactivity in the lung tissue was measured, two peaks of DNA synthesis in the lung were observed in a day under the short light/dark cycle, and both peaks were during light periods, while only one peak was observed during the dark period under the standard light/dark cycle. Although the level of [3H]thymidine incorporation into the lung tissue in the short light/dark cycle is lower than that in the standard cycle, frequent or unbalanced DNA synthesis may have promoted the growth of lung tumors.
authors.affiliation: Department of Radiation Biology, Faculty of Medicine, Osaka University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nakajima
authors.forename: I
authors.initials: I
authors.lastname: Narama
authors.forename: T
authors.initials: T
authors.lastname: Matsuura
authors.forename: T
authors.initials: T
authors.lastname: Nomura
mesh_terms: D000236:Adenoma / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D004273:DNA, Neoplasm / Q000096:biosynthesis; D008175:Lung Neoplasms / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008805:Mice, Inbred A; D017440:Photoperiod; D014520:Urethane
chemical_list: D004273:DNA, Neoplasm; D014520:Urethane