title: Studies on cytogenesis in adult rat adrenal cortex: circadian and zonal variations and their modulation by adrenocorticotropic hormone.
abstract: Circadian rhythms and zonal variations in the cell proliferation of adult rat adrenal cortex were studied by following the cells in the DNA-synthesizing stage (S-phase) as assessed by 5-bromo-2'-deoxyuridine incorporation into the cell-nuclei and/or by visualizing proliferating cell nuclear antigen. The S-phase cells were observed throughout the day in two regions of the adrenal cortex: (i) a region from the inner half of the zona glomerulosa to near the outer margin of the zona fasciculata, and (ii) the outer one-fourth portion of the zona fasciculata. Very little change in number was observed in the former region between day and night, while a burst of cell proliferation occurred in early morning at 3-4 a.m. in the latter region. A prominent rise in the plasma adrenocorticotropic hormone (ACTH) concentration preceded the burst of cell proliferation by about 4 h. Upon raising the plasma ACTH concentration by administration of ACTH or metyrapone, prominent cell proliferation also occurred in the same portion of the zona fasciculata 4-6 h after the provoked ACTH surge. Thus at least two sites in rat adrenal cortex are responsible for cytogenesis in this endocrine organ, and respond differentially to day/night cycles and circulating ACTH levels.
authors.affiliation: Department of Biochemistry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Miyamoto
authors.forename: F
authors.initials: F
authors.lastname: Mitani
authors.forename: K
authors.initials: K
authors.lastname: Mukai
authors.forename: M
authors.initials: M
authors.lastname: Suematsu
authors.forename: Y
authors.initials: Y
authors.lastname: Ishimura
mesh_terms: D000302:Adrenal Cortex / Q000166:cytology*; D000324:Adrenocorticotropic Hormone / Q000502:physiology*; D000818:Animals; D002455:Cell Division; D002940:Circadian Rhythm; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000324:Adrenocorticotropic Hormone