Age-related variation in circadian rhythms of mitosis in the adrenal cortex of the male rat.
Using a metaphase arrest technique, mitotic activity was quantified in the adrenal cortex over a 24-h period in 14-day-old male Sprague-Dawley rats before functional rhythmicity of the hypothalamic pituitary-adrenal (HPA) axis is established, and after its onset, in 6- to 7-week-old rats. At all times, proliferative activity was greater in the younger animals, as previously reported. A significant circadian rhythm was identified in both groups, but the timing of the peak differed, lying between 17.00 and 21.00 h at 14 days and 11.00 and 15.00 h at 6-7 weeks. These results raise the possibility that functional rhythmicity of the HPA axis may alter an inherent proliferative rhythm.
McNicol
A M
AM
University Department of Pathology, Glasgow Royal Infirmary.
Penman
I D
ID
Duffy
A E
AE
D000302:Adrenal Cortex / Q000166:cytology*; D000367:Age Factors; D000818:Animals; D002940:Circadian Rhythm; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D008297:Male; D008938:Mitosis; D010913:Pituitary-Adrenal System / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors