title: Postnatal development of the circadian rhythm of circulating blood cells in rats.
abstract: In the present study the variations in the leukocyte and erythrocyte counts were investigated in the peripheral blood within the light and darkness periods during the postnatal development of rats. The animals were kept under an artificial illumination regime (12 hours light, 12 hours darkness), and examined at the ages of 7, 14, 21, 28, 35 and 45 days, and in maturity (56 days). Erythrocyte counts exhibited no light-dark rhythm. The circadian rhythm of leukocyte counts developed in male and female laboratory rats in the fourth week of age.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D001773:Blood Cells / Q000502:physiology*; D002940:Circadian Rhythm; D004906:Erythrocyte Count; D005260:Female; D007958:Leukocyte Count; D008297:Male; D051381:Rats