DIURNAL-VARIATION OF MITOTIC RESPONSE IN EPITHELIUM AT EDGE OF ACUTE ULCERS IN RECTAL MUCOUS-MEMBRANE OF GUINEA-PIGS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 125  (FEB) , 337-348
Abstract
The diurnal mitotic rhythm of wounded rectal epithelial cells in the guinea pig was compared with the rat. The mitotic response to wounding was examined in ulcers resulting from the excision of small pieces of rectal mucous membrane in 2 groups of guinea pigs. Mitotic counts were carried out in the glandular epithelium at the ulcer edges at 2 h intervals over 24 h. Mitotic activity increased in 2-4 h and thereafter showed a peak-and-trough pattern. The wounded rectal epithelial cells exhibited a diurnal variation with a peak of activity during the day and low activity at night. Such diurnal rhythmicity is apparently not species-specific because it was similar in both the guinea pig and rat and there is probably not a chalone-adrenaline complex in the rectal epithelium since the diurnal variation was similar in the nocturnal rat and in the diurnal guinea pig, and was not abolished by wounding. Mitotic activity was lower in the glands at the immediate wound edge, and in the upper cells of the glands. The cells in these situations are probably designated for migration to close the defect, for migration excludes mitosis. The mechanisms responsible for the circadian rhythm of mitosis are possibly different from those which induce the bursts of mitotic activity after wounding. If this is true it would be contrary to the chalone concept.