Studies on cytogenesis in adult rat adrenal cortex: Circadian and zonal variations and their modulation by adrenocorticotropic hormone

Hirokuni Miyamoto, Fumiko Mitani, Kuniaki Mukai, Makoto Suematsu, Yuzuru Ishimura

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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.

Original languageEnglish
Pages (from-to)1175-1183
Number of pages9
JournalJournal of biochemistry
Issue number6
Publication statusPublished - 1999 Jan 1



  • Adrenal cortex
  • Adrenocorticotropic hormone (ACTH)
  • Circadian rhythm
  • Proliferation

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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