Differential effects of oestrogenic hormones on cell proliferation in the colonic crypt epithelium and in colonic carcinomata of rats.

A number of hormones, including some steroids, have previously been shown to influence the rate of cell division in the colonic crypt epithelium and in colonic tumours. In this report the effect of oophorectomy and of treatment with ovarian hormones on cell proliferation in these tissues is compared. Colonic tumours cell proliferation was retarded following oophorectomy and this retardation was reversed by the administration of oestradiol, but not by the administration of progesterone. Oophorectomy did not retard cell proliferation in the colonic crypts. The possible significance of these findings in relation to age-dependent variations in the sex ratio for human bowel cancer is discussed.