Histological studies on the regeneration of small-intestine epithelium of rats irradiated with sublethal doses of X rays.

The dynamics of regeneration of small-intestine epithelium was studied in rats irradiated with X-rays in sublethal doses of 550, 600 or 750 R. Sixty-two irradiated and 22 control animals were used in the experiment. They were killed 1,2,4,6,8,14 and 25 days after the irradiation. Specimens of duodenum and jejunum were examined histologically, the sections being stained with H.E. and p.a.S. Already 1 and 2 days after irradiation the intestinal villi became shorter and deformed. The blood vessels were damaged, the enterocytes showed features of degeneration and vocuolization, the epithelium was detached by the exudate which accumulated in the stroma. Irradiation markedly disturbed the regeneration of intestinal epithelium in the period from the 1st to the 6th day. Cytological calculations indicate that on the 1st and 2nd days after irradiation the number of epithelial cells of the villi, and particularly of young cryptal ones, markedly dropped. On the 4th and 6th days increased proliferation of young cryptal cells considerably surpassed the physiological rate. The accompanying disturbances in differentiation consisted in a decreased acidophilic to basophilic cells ratio and in retardation of maturation of goblet cells. The absolute number of goblet cells was increased, as well as their proportion to the number of enterocytes.