title: Morphological alterations and NO-synthase expression in the heart after continuous light exposure of rats.
abstract: Although exposure to continuous light is associated with hypertension and modulates the outcome of ischemia-reperfusion injury, less attention has been paid to its effects on cardiac morphology. We investigated whether 4-week exposure of experimental rats to continuous 24 h/day light can modify cardiac morphology, with focus on heart weight, fibrosis and collagen I/III ratio in correlation with NO-synthase expression. Two groups of male adult Wistar rats were studied: controls exposed to normal light/dark cycle (12 h/day light, 12 h/day dark) and rats exposed to continuous light. After 4 weeks of treatment the absolute and the relative heart weights were determined and myocardial fibrosis and collagen type I/III ratio were evaluated using picrosirius red staining. Endothelial and inducible NO-synthase expression was detected immunohistochemically. The exposure of rats to continuous light resulted in an increase of body weight with proportionally increased heart weight. Myocardial fibrosis remained unaffected but collagen I/III ratio increased. Neither endothelial nor inducible NO-synthase expression was altered in light-exposed rats. We conclude that the loss of structural homogeneity of the myocardium in favor of collagen type I might increase myocardial stiffness and contribute to functional alterations after continuous light exposure.
authors.affiliation: Institute of Pathophysiology, School of Medicine, Comenius University, Bratislava, Slovak Republic. ludo@lfuk.sk
authors.forename: L
authors.initials: L
authors.lastname: Paulis
authors.forename: R
authors.initials: R
authors.lastname: Vazan
authors.forename: F
authors.initials: F
authors.lastname: Simko
authors.forename: O
authors.initials: O
authors.lastname: Pechánová
authors.forename: J
authors.initials: J
authors.lastname: Styk
authors.forename: P
authors.initials: P
authors.lastname: Babál
authors.forename: P
authors.initials: P
authors.lastname: Janega
mesh_terms: D000818:Animals; D001835:Body Weight / Q000528:radiation effects; D024042:Collagen Type I / Q000378:metabolism; D024061:Collagen Type III / Q000378:metabolism; D005355:Fibrosis; D008027:Light; D008297:Male; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000473:pathology / Q000528:radiation effects*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D009929:Organ Size / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors