title: Pineal ablation in varying photoperiods and the incidence of 9,10-dimethyl-1,2-benzanthracene induced mammary cancer in rats.
abstract: Our earlier observation of increased incidence of 9,10-dimethyl-1,2-benzanthracene (DMBA) induced mammary carcinoma in young, virgin 'functionally' pinealectomized Holtzman rats poses the question whether or not a comparable incidence would occur in surgically pinealectomized rats reared in varying photoperiods (e.g. light/dark (LD) 24/0 or LD 10/14 schedules). Results show that functionally or surgically pinealectomized rats in LD 24/0 schedule have comparable mammary tumor incidence (95% and 83%, respectively) and latency period of tumor appearance (60 +/- 3.1 and 69.2 +/- 6.6 days, respectively). However, when surgically pinealectomized rats were kept in short photoperiods (LD 10/14), a significant difference was observed in both tumor incidence (60.9%) and latency period (91.8 +/- 11.0 days). Our data suggest that the susceptibility of the mammary gland to carcinogenic insult may be modulated by the concentration of the pineal hormone, melatonin, in the CNS.
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000230:Adenocarcinoma / Q000139:chemically induced; D000818:Animals; D000831:Animals, Newborn; D001551:Benz(a)Anthracenes / Q000633:toxicity*; D004198:Disease Susceptibility; D005260:Female; D008027:Light; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced*; D010870:Pineal Gland / Q000502:physiology*; D051381:Rats; D013997:Time Factors
chemical_list: D001551:Benz(a)Anthracenes; D015127:9,10-Dimethyl-1,2-benzanthracene