Effect of hypophysectomy on mitotic proliferation in gastric epithelium

¹ Department of Anatomy, The University of Michigan Medical School, Ann Arbor, Michigan

Mitotic division of surface mucous cells and of mucous neck cells in the stomach followed a circadian periodicity in rats kept under standardized conditions with exposure to light from 6 am to 6 pm. The greatest activity occurred between 4 am and 10 am and the least at 12 midnight. Circadian periodicity persisted after pituitary excision. Following hypophysectomy, mitotic activity in surface cells was increased during the daytime, with no effect being observed at night. After hypophysectomy mitotic activity of mucous neck cells was depressed at 2 am and 8 am with no change being observed at 12 noon, 2 pm, or 8 pm. When colchicine was given over a 6-hr period during the day to increase the number of countable mitoses, mitotic activity was increased in surface cells and decreased in the mucous neck cells in hypophysectomized rats.

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