title: Influences of light-dark shifting on the immune system, tumor growth and life span of rats, mice and fruit flies as well as on the counteraction of melatonin.
abstract: Animal models were designed to study the changes in immune function, oncogenicity and life span of rats, mice and fruit flies following light-dark (LD) shift manipulations. Alternating the photoperiod of LD 14:10 and DL 10:14 every 3 days in rats disrupted the circadian immune rhythm pattern, decreased the blood leukocyte concentration by 48% and lowered the percentage of lymphocytes in the blood from 71% (control) to 49.2%. In mice, the phagocytosis of neutrophils was only reduced by 7%, but the level of serum hemolysin dropped significantly in the photoperiod-shifted group as compared with animals kept under a constant photoperiod of LD 12:12 or LD 14:10. In Ehrlich-carcinoma- or sarcoma-180-injected mice, a reduction of survival duration, acceleration of tumor growth and depression of the immune system were recorded in the LD-shifted animals. In addition, the life span of fruit flies was shortened by 9.6% by photoperiodic shifting. Melatonin treatment evidently counteracted the deleterious influences of photoperiodic shifting in the above animals. It is suggested that repeated inversion of the LD cycle results in a chronobiological abnormality that, in turn, induces dysfunctions. Reentrainment by exogenous melatonin may inhibit the harmful influences of photoperiodic shifting.
authors.affiliation: Department of Physiology, Shenyang Pharmaceutical University, China.
authors.forename: J C
authors.initials: JC
authors.lastname: Li
authors.forename: F
authors.initials: F
authors.lastname: Xu
mesh_terms: D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000473:pathology; D002909:Chronobiology Phenomena; D002940:Circadian Rhythm / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects; D004331:Drosophila melanogaster; D007107:Immune System / Q000187:drug effects* / Q000528:radiation effects*; D008136:Longevity / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects*; D008297:Male; D008550:Melatonin / Q000494:pharmacology* / Q000502:physiology; D051379:Mice; D009374:Neoplasms, Experimental / Q000473:pathology*; D017440:Photoperiod; D051381:Rats; D017207:Rats, Sprague-Dawley; D012510:Sarcoma 180 / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects
chemical_list: D008550:Melatonin