Effects of uterine distension and oestradiol on cell kinetics in the endometrial epithelium of ovariectomized rats.

Cell kinetics in the uterine epithelium of ovariectomized rats were studied after uterine distension and/or an oestradiol injection, by cumulative 3H-TdR labelling and percentage of labelled mitoses (PLM). With both methods it was found that distension shortens the total cell cycle at the expense of G1 more than does oestradiol. Both treatments act in a cumulative manner since the greatest reduction in T c is observed after distension plus oestradiol. PLM curves showed that distension and/or oestradiol induce a 30% reduction S phase duration. The evolution of percentages of labelled cells and colchicine-blocked mitoses after these treatments confirms their additive effects and indicates that the mitogenic action of oestradiol is delayed compared to that of distension. It is suggested that these factors stimulate epithelial cell division in the uterus through partly different metabolic channels.