title: Effect of constant light on fetal and maternal prolactin rhythms in sheep.
abstract: A 24-h rhythm of plasma PRL is present in fetal sheep. This rhythm is synchronized to an environmental clue (zeitgeber). We determined whether the light-dark cycle (L:D) is a zeitgeber for the fetal PRL rhythm and, if so, whether the mother might convey this zeitgeber to the fetus. We kept nine ewes (twin pregnancies) in constant light (L:L) and five ewes (singleton) in 14:10 L:D from 110 days gestation. Fetuses and mothers were catheterized at 119 days gestation. Blood samples were taken hourly for 24 h after 16 days under L:L or L:D. A mean 24-h rhythm of PRL was found (by RIA) in fetuses under L:D, but not in those under L:L. However, fetuses under L:L showed individual 24-h PRL rhythms (cosinor analysis) whose acrophases were distributed around the clock. Nonsynchronized rhythms persisted after 23 and 30 days of L:L. Acrophases of PRL rhythms within a set of twins were closer than those between sets, suggesting that twins were responding to a common signal. These findings indicate that the L:D cycle is a zeitgeber for the PRL rhythm in fetal sheep and suggest that the mother might convey the zeitgeber.
authors.affiliation: Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: V H
authors.initials: VH
authors.lastname: Parraguez
authors.forename: G J
authors.initials: GJ
authors.lastname: Valenzuela
authors.forename: M
authors.initials: M
authors.lastname: Vergara
authors.forename: C A
authors.initials: CA
authors.lastname: Ducsay
authors.forename: S M
authors.initials: SM
authors.lastname: Yellon
authors.forename: M
authors.initials: M
authors.lastname: Serón-Ferré
mesh_terms: D000818:Animals; D001683:Biological Clocks; D002940:Circadian Rhythm; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D006321:Heart / Q000196:embryology / Q000502:physiology; D008027:Light; D008168:Lung / Q000196:embryology / Q000502:physiology; D017440:Photoperiod; D011247:Pregnancy; D011388:Prolactin / Q000097:blood*; D012756:Sheep
chemical_list: D011388:Prolactin