title: Circadian variations of plasma atrial natriuretic peptide and corticosterone in rats with continuous or restricted access to food.
abstract: In the present study plasma Atrial Natriuretic Peptide (ANP) and Corticosterone (B) levels were determined in 2 groups of Wistar rats, a Control group (C) with free access to food, and a Food Shift group (FS) with access to food only from 0900 to 1100 h for 2 weeks. Blood samples were collected by decapitation at 4 hour intervals. ANOVA indicated that B varied over time in both groups (F (6.46) = 10.14, p < 0.0001 for C and F (6.5) = 5.10, p = 0.0005 for FS). There was also time variation in plasma ANP levels in both groups (F (6.54) = 3.78, p = 0.003 for C and F (6.48) = 2.73, p = 0.02 for FS group). Plasma B presented circadian variations from 78 +/- 17 nmol/l (mean +/- SEM) at 0800 h to 339 +/- 79 nmol/l at 2000 h. The day peak plasma ANP level (pmol/l) was also attained at 2000 h (68 +/- 19). This value was higher than all others measured throughout the day. The restricted feeding regimen resulted in a 12 hour shift of peak B values (395 +/- 39 vs 125 +/- 24). The FS rats presented the highest ANP level at 0800 h. The present study indicates similar circadian variations of plasma ANP and B in rats on an ad lib or restricted feeding regimen. ANP and B secretion may occur in anticipation of the feeding period or day activity.
authors.forename: M H
authors.initials: MH
authors.lastname: Oliveira
authors.forename: J
authors.initials: J
authors.lastname: Antunes-Rodrigues
authors.forename: A M
authors.initials: AM
authors.lastname: Leal
authors.forename: L L
authors.initials: LL
authors.lastname: Elias
authors.forename: A C
authors.initials: AC
authors.lastname: Moreira
mesh_terms: D000704:Analysis of Variance; D000821:Animal Feed; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood*; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood*; D005508:Food Deprivation / Q000502:physiology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009320:Atrial Natriuretic Factor; D003345:Corticosterone